Coalescing adjacent gather/scatter operations

ABSTRACT

According to one embodiment, a processor includes an instruction decoder to decode a first instruction to gather data elements from memory, the first instruction having a first operand specifying a first storage location and a second operand specifying a first memory address storing a plurality of data elements. The processor further includes an execution unit coupled to the instruction decoder, in response to the first instruction, to read contiguous a first and a second of the data elements from a memory location based on the first memory address indicated by the second operand, and to store the first data element in a first entry of the first storage location and a second data element in a second entry of a second storage location corresponding to the first entry of the first storage location.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/976,228, filed on Dec. 21, 2015, entitled “COALESCINGADJACENT GATHER/SCATTER OPERATIONS”, which is a continuation of U.S.patent application Ser. No. 13/997,784, filed on Jun. 25, 2013, entitled“COALESCING ADJACENT GATHER/SCATTER OPERATIONS”, now U.S. Pat. No.9,348,601, Issued on May 24, 2016, which is hereby incorporated hereinby this reference in its entirety and for all purposes. U.S. patentapplication Ser. No. 13/997,784 is itself a U.S. National PhaseApplication under 35 U.S.C. §371 of International Application No.PCT/US2012/071688, filed Dec. 26, 2012, entitled “COALESCING ADJACENTGATHER/SCATTER OPERATIONS”.

TECHNICAL FIELD

The field of invention relates generally to processor architecture, and,more specifically, to techniques for coalescing gather scatteroperations.

BACKGROUND ART

In order to fully utilize the single instruction, multiple data (SIMD)processor, gather instructions are used to read a set of (possibly)non-contiguous source data elements from memory and pack them together,typically into a single register. Scatter instructions do the reverse.In some instances, the data elements in memory are known to becontiguous to each other. Unfortunately, conventional gather and scatterinstructions do not leverage off this known information, thus reducingthe efficiency of the SIMD processor.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1A illustrates a snippet of a source code.

FIG. 1B illustrates the resulting gather/scatter operations when theload/store instructions of the source code of FIG. 1A are vectorized.

FIG. 2 is a block diagram of an execution pipeline of a processor orprocessor core according to one embodiment of the invention.

FIGS. 3A through 3E are block diagrams illustrating the coalescing ofthree adjacent gather instructions.

FIG. 4 is a block diagram illustrating the coalescing of three adjacentgather instructions with a writemask.

FIG. 5 is a flow chart illustrating a method for processing a coalescedgather instruction.

FIG. 6 is a flow chart illustrating in further details the method ofFIG. 5.

FIG. 7 is a block diagram illustrating the coalescing of three adjacentscatter instructions.

FIGS. 8A through 8H are block diagrams illustrating an embodiment ofcoalescing adjacent gather instructions using current ISA.

FIG. 9A illustrates the pseudo-code for the operation of a newinstruction vgatherp0123 qpd.

FIG. 9B illustrates the pseudo-code for the operation of a newinstruction vgatherp4567 qpd.

FIG. 10A illustrates the pseudo-code for the operation of a newinstruction vgatherp01 qpd.

FIG. 10B illustrates the pseudo-code for the operation of a newinstruction vgatherp23 qpd.

FIG. 10C illustrates the pseudo-code for the operation of a newinstruction vgatherp34 qpd.

FIG. 10D illustrates the pseudo-code for the operation of a newinstruction vgatherp67 qpd.

FIG. 11A is a block diagram of the GENMUX unit for transposing the Xcomponents of the VPU banks.

FIG. 11B is a block diagram of the GENMUX unit for transposing the Ycomponents of the VPU banks.

FIG. 12A illustrates an advanced vector extensions (AVX) instructionformat according to one embodiment of the invention.

FIG. 12B illustrates an advanced vector extensions (AVX) instructionformat according to another embodiment of the invention.

FIG. 12C illustrates an advanced vector extensions (AVX) instructionformat according to another embodiment of the invention.

FIG. 13A is a block diagram illustrating a generic vector friendlyinstruction format and class A instruction templates thereof accordingto embodiments of the invention.

FIG. 13B is a block diagram illustrating the generic vector friendlyinstruction format and class B instruction templates thereof accordingto embodiments of the invention.

FIG. 14A is a block diagram illustrating a specific vector friendlyinstruction format according to one embodiment of the invention.

FIG. 14B is a block diagram illustrating a generic vector friendlyinstruction format according to another embodiment of the invention.

FIG. 14C is a block diagram illustrating a generic vector friendlyinstruction format according to another embodiment of the invention.

FIG. 14D is a block diagram illustrating a generic vector friendlyinstruction format according to another embodiment of the invention.

FIG. 15 is a block diagram of register architecture according to oneembodiment of the invention.

FIG. 16A is a block diagram illustrating both an in-order pipeline and aregister renaming, out-of-order issue/execution pipeline according toembodiments of the invention.

FIG. 16B is a block diagram illustrating both an embodiment of anin-order architecture core and a register renaming, out-of-orderissue/execution architecture core to be included in a processoraccording to embodiments of the invention.

FIG. 17A is a block diagram of a processor core according to oneembodiment of the invention.

FIG. 17B is a block diagram of a processor core according to anotherembodiment of the invention.

FIG. 18 is a block diagram of a processor according to embodiments ofthe invention.

FIG. 19 is a block diagram of a system in accordance with one embodimentof the invention.

FIG. 20 is a block diagram of a more specific system in accordance withan embodiment of the invention.

FIG. 21 is a block diagram of a more specific system in accordance withanother embodiment of the invention.

FIG. 22 is a block diagram of a SoC in accordance with an embodiment ofthe invention.

FIG. 23 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention.

DETAILED DESCRIPTION

Various embodiments and aspects of the inventions will be described withreference to details discussed below, and the accompanying drawings willillustrate the various embodiments. The following description anddrawings are illustrative of the invention and are not to be construedas limiting the invention. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentinvention. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present inventions.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin conjunction with the embodiment can be included in at least oneembodiment of the invention. The appearances of the phrase “in oneembodiment” in various places in the specification do not necessarilyall refer to the same embodiment.

FIG. 1A illustrates a snippet of a source code. A very common pattern insource codes, as illustrated in FIG. 1A, is loading and storingcontiguous elements of a structure into a sequence of registers. Whenthe source code of FIG. 1A is vectorized, each of the loads becomes agather operation, and each of the stores becomes a scatter operation, asillustrated in FIG. 1B.

Referring now to FIG. 1B, gather operation 1 will perform eight memoryreads, distributed through memory according to the eight indices inregister zmm8. Gather operation 2 uses the same base (rax) and indices(zmm8), and performs almost exactly the same memory reads as gatheroperation 1, except it is offset by 8 bytes (because gather operation 2has a displacement operand of 8). Gather operation 3 will perform thesame memory reads as gather operation 1, except it is offset by 16 bytes(because gather operation 2 has a displacement operand of 16). Thus, thethree gather operations produce a total of twenty four reads goingthrough a memory execution cluster (MEC). The three gather operationsalso require the gather/scatter state machine (details to be providedbelow) to set up three times, which takes a significant number of cyclesand transfers between a vector processing unit (VPU) and MEC.

Referring still to FIG. 1B, scatter operation 1 will perform eightmemory writes, distributed through memory according to the eight indicesin zmm8. Scatter operation 2 uses the same base (rax) and indices(zmm8), and performs almost exactly the same memory writes as scatteroperation 1, except it is offset by 8 bytes (because scatter operation 2has a displacement operand of 8). Scatter operation 3 will perform thesame memory writes as scatter operation 1, except it is offset by 16bytes (because scatter operation 2 has a displacement operand of 16).Thus, the three scatter operations produce a total of twenty four writesgoing through a memory execution cluster (MEC). The three scatteroperations also require the gather/scatter state machine to set up threetimes, which takes a significant number of cycles and transfers betweenthe VPU and MEC.

According to some embodiments, a new instruction set architecture (ISA)is utilized to perform coalesced gathering of contiguous data elementsfrom memory and storing them into a set of multiple destinationregisters. The new ISA is also utilized to perform coalesced scatteringof data elements from multiple source operands (e.g., registers, memorylocations) by storing them in contiguous data elements in memory. A newset of processor instructions is used to implement the coalescedgathering/scattering with significant performance improvement withrespect to existing processor instructions. The ISA is defined tooperate on 128-bit SIMD registers (e.g., XMM registers), 256-bit SIMDregisters (e.g., YMM registers), or 512-bit SIMD registers (e.g., ZMMregisters). The SIMD register width discussed above are only forillustrative purposes. It will be appreciated that other the ISA may bedefined to operate with other SIMD register widths. Embodiments ofcoalesced gathering techniques include reading from memory, using asingle memory access, contiguous data elements and storing them inmultiple destination storage locations. Embodiments of coalescedscattering techniques include reading data elements from multiple sourceregisters, and storing them in memory contiguously in a single memoryaccess. In the description provided herein, contiguous data elementsshall mean that the data elements are located adjacent to each other inmemory. Thus, the location in memory corresponding to the end of onedata element is adjacent to the location in memory corresponding to thestart of another data element.

FIG. 2 is a block diagram of a processor or processor core according toone embodiment of the invention. Referring to FIG. 2, processor 200 mayrepresent any kind of instruction processing apparatuses or processingelements. A processing element refers to a thread, a process, a context,a logical processor, a hardware thread, a core, and/or any processingelement, which shares access to other shared resources of the processor,such as reservation units, execution units, pipelines, and higher levelcaches/memory. A physical processor typically refers to an integratedcircuit, which potentially includes any number of other processingelements, such as cores or hardware threads. A core often refers tologic located on an integrated circuit capable of maintaining anindependent architectural state, where each independently maintainedarchitectural state is associated with at least some dedicated executionresources. In one embodiment, processor 200 may be a general-purposeprocessor. Processor 200 may be any of various complex instruction setcomputing (CISC) processors, various reduced instruction set computing(RISC) processors, various very long instruction word (VLIW) processors,various hybrids thereof, or other types of processors entirely.Processor 200 may also represent one or more processor cores.

In one embodiment, processor 200 includes, but is not limited to,instruction decoder 202 to receive and decode instruction 210.Instruction decoder 202 may generate and output one or moremicro-operations, micro-code, entry points, microinstructions, otherinstructions, or other control signals, which reflect, or are derivedfrom, instruction 210. Instruction decoder 202 may be implemented usingvarious different mechanisms. Examples of suitable mechanisms include,but are not limited to, microcode read only memories (ROMs), look-uptables, hardware implementations, programmable logic arrays (PLAs), andthe like.

Execution units 204, which may include an arithmetic logic unit (ALU),or another type of logic unit capable of performing operations based oninstructions. As a result of instruction decoder 202 decoding theinstruction 210, execution unit 204 may receive one or moremicro-operations, micro-code entry points, microinstructions, otherinstructions, or other control signals, which reflect, or are derivedfrom, the instructions. Execution unit 204 may be operable as a resultof instructions indicating one or more source operands (SRC) and tostore a result in one or more destination operands (DEST) of a registerset indicated by the instructions. Execution unit 204 may includecircuitry or other execution logic (e.g., software combined withhardware and/or firmware) operable to execute instructions or othercontrol signals derived from the instructions and perform an operationaccordingly.

In one embodiment, instruction 210 may implicitly indicate and/orexplicitly specify (e.g., through one or more dedicated fields or setsof bits) the source and destination operands. Examples of suitablesources and/or destination of the operands include registers, memory,immediate of the instruction, and combinations thereof. In variousembodiments, the source and destination operands may be 8-bit, 16-bit,32-bit, 64-bit, 128-bit, 256-bit, or 512-bit operands, although this isnot required.

Some or all of the source and destination operands may be stored instorage resources 206 such as registers of a register set or memory. Aregister set may be part of a register file, along with potentiallyother registers, such as status registers, flag registers, etc. Aregister may be a storage location or device that may be used to storedata. The register set may often be physically located on die with theexecution unit(s). The registers may be visible from the outside of theprocessor or from a programmer's perspective. For example, instructionsmay specify operands stored in the registers. Various different types ofregisters are suitable, as long as they are capable of storing andproviding data as described herein. The registers may or may not berenamed Examples of suitable registers include, but are not limited to,dedicated physical registers, dynamically allocated physical registersusing register renaming, combinations of dedicated and dynamicallyallocated physical registers, etc. Alternatively, one or more of thesource and destination operands may be stored in a storage locationother than a register, such as, for example, a location in systemmemory.

According to one embodiment, execution unit 204 includes gather/scatterunit 208 that executes gather/scatter instructions that have beendecoded by instruction decoder 202. Below are embodiments of gatheringand scattering instructions, which when executed by gather/scatter unit208, improve efficiency of a SIMD system by taking advantage of the factthat data elements are contiguously located in memory.

In one embodiment, the gather instruction is a coalesced gatherinstruction. The execution of this instruction by gather/scatter unit208 stores contiguous data elements from memory into multipledestination operands. For example, in some embodiments, up to sixteen32-bit or eight 64-bit floating-point data elements are conditionallypacked into destination operands such as XMM, YMM, or ZMM registers.

The contiguous memory data elements to be loaded into destinationoperands are specified via a type of SIB (scale, index, and base)addressing. The coalesced gather instruction also includes a writemask.In some embodiments that use a dedicated mask register such as a “k”writemask (detailed later), the memory data elements will be loaded whentheir corresponding writemask bit indicates that they should be (forexample, in some embodiments if the bit is a “1”). If a memory dataelement's corresponding writemask bit is not set, the corresponding dataelement of the destination operand (e.g., an XMM, YMM, or ZMM register)is left unchanged.

In one embodiment, the execution of a coalesced gather instruction willresult in the entire writemask register being set to zero unless thereis an exception. However, in some embodiments the instruction issuspended by an exception if at least one element has already beengathered (i.e., if the exception is triggered by an element other thanthe least significant one with its writemask bit set). When this happensthe destination register and the writemask register are partiallyupdated (those elements that have been gathered are placed into thedestination register and have their mask bits set to zero). If any trapsor interrupts are pending from already gathered elements, they may bedelivered in lieu of the exception and the EFLAGS resume flag orequivalent is set to one so an instruction breakpoint is notre-triggered when the instruction is continued.

In some embodiments with 128-bit size destination registers, theinstruction will gather up to four single-precision floating pointvalues or two double-precision floating point values per destinationregister. In some embodiments with 256-bit size destination registers,the instruction will gather up to eight single-precision floating pointvalues or four double-precision floating point values per destinationregister. In some embodiments with 512-bit size destination registers,the instruction will gather up to sixteen single-precision floatingpoint values or eight double-precision floating point values perdestination register.

In some embodiments, if the mask and destination registers are the same,this instruction delivers a general protection (GP) fault. Typically,the data element values may be read from memory in any order. However,faults are delivered in a right-to-left manner That is, if a fault istriggered by an element and delivered, all elements closer to the leastsignificant bit (LSB) of the destination XMM, YMM, or ZMM will becompleted (and non-faulting). Individual elements closer to the MSB mayor may not be completed. If a given element triggers multiple faults,they are delivered in the conventional order. A given implementation ofthis instruction is repeatable—given the same input values andarchitectural state, the same set of elements to the left of thefaulting one will be gathered.

The coalesced gather instruction may be implemented in several formats.In one embodiment, the coalesced gather instruction is defined asfollows:

-   -   VGATHERQ4PD zmm3:zmm5:zmm6:zmm0{k1}, {rax+zmm9}//Format 0

where zmm3, zmm5, zmm6, and zmm0 are destination vector registeroperands (such as a 128-, 256-, 512-bit register, etc.), k1 is awritemask operand (such as a 16-bit register examples of which aredetailed later), rax is the base address, and zmm9 is a vector/array ofindices. Note that the above format is described for illustrationpurposes only; other formats or orders of the operands may beimplemented. In one embodiment, the base and a value stored in an indexof the vector of indices are used to generate a memory addresscorresponding to the starting location of a block of contiguous dataelements which are read and stored into the corresponding data elements(i.e., entries) of the destination operands. In some embodiments, thewritemask is also of a different size (8 bits, 32 bits, etc.).Additionally, in some embodiments, not all bits of the writemask areutilized by the instruction.

In one embodiment, in the above format 0 of the instruction, the firstdestination operand is zmm3, the second destination operand is zmm5, thethird destination operand is zmm6, and the fourth destination operand iszmm0 In another embodiment, the order of the operands is the reverse. Inone embodiment, the order of these operands explicitly indicates theorder in which contiguous data elements in memory will be loaded intothe destination operands. Thus, in the above format 0 example, assumingthe writemask indicates all data elements are to be updated (discussedin further details below), and assuming further that zmm3 is the firstoperand, data element at memory location “rax+zmm9{0}” is stored intozmm3{0}. The next three contiguous data elements, i.e., data elements atmemory location “rax+zmm9{0}+size of(data element)”, at“rax+zmm9[0]+(2*size of(data element))”, and at “rax+zmm9[0]+(3*sizeof(data element))” are stored into the first data element of each of thesubsequent destination operands, i.e., zmm5[0], zmm6[0], and zmm0[0],respectively. The second data element of each destination operand willbe updated with contiguous data elements in memory using the sameaddressing scheme, e.g., zmm3[1] will be updated with the data elementat memory location “rax+zmm9[1]”, and zmm5[1], zmm6[1], zmm0[1] will beloaded with the next three contiguous data elements in memory.

VGATHERQ4PD is the instruction's opcode. Typically, each operand isexplicitly defined in the instruction. The size of the data elements maybe defined in the “suffix” of the instruction. For instance, the suffix“PD” in the instruction VGATHERQ4PD may indicate that the data elementis a double precision (i.e., 64 bits). In most embodiments, dataelements are either 32 or 64 bits. If the data elements are 32 bits insize, and the operands are 512 bits in size, then there are sixteen (16)data elements per operand. In some embodiments, the number of dataelements per operand implicitly indicates the number of indices that arepresent in the vector of indices (e.g., zmm9 in the above example.) Insome embodiments, the number of operands is also explicitly defined inthe instruction. For instance, in the above example, the “4” precedingthe “PD” suffix may indicate that the instruction is coalescing fouradjacent gather operations, i.e., the execution of the instructionresults in writing four contiguous data elements from memory intocorresponding data elements of four destination operands (e.g., zmm3,zmm5, zmm6, and zmm0 in the above example). In one embodiment, the blockof contiguous data elements are read from memory in a single memoryaccess. In one embodiment, the block of data elements are stored intoall the destination operands in a single cycle.

In another embodiment, the coalesced gather instruction is defined asfollows:

-   -   VGATHERQ4PD zmm3-zmm0 {k1}, {rax+zmm9}.//Format 1

The execution of the coalesced gather instruction having format 1 causesoperations similar to those discussed above in the text relating toformat 0 to be executed. The difference between format 0 and format 1 isthat with format 1, the destination registers are specified as a rangeof registers. In the above example of format 1, the range of destinationregisters are bound by zmm3 and zmm0 Thus, implicitly, the destinationregisters are zmm3, zmm2, zmm1, and zmm0, where zmm2 and zmm1 areimplied by the fact that the instruction explicitly indicates fourdestination registers are to be packed with data elements from memory.Note that in this embodiment, although the choice of the firstdestination register may be freely specified, it is a syntax error tospecify a range of destination registers that is inconsistent with thenumber of destination registers explicitly indicated by the instruction.

In another embodiment, the coalesced gather instruction is defined asfollows:

-   -   VGATHERQ4PD zmm3-zmm0{k1}, {rax+zmm9}.//Format 2

The execution of the coalesced gather instruction having format 2 causesoperations similar to those discussed above in the text relating toformat 0 to be executed. The difference between format 0 and format 2 isthat with format 2, the destination registers are fixed. Thus, forinstance, in the above example, the destination registers are fixed tozmm3, zmm2, zmm1, and zmm0 because the instruction explicitly indicatesfour destination registers are to be packed with data elements frommemory. Note that in this embodiment, it is a syntax error to specifyany destination registers other than “zmm3-zmm0” and this is specifiedonly as an aid to readability. Although in the above example, theregisters are fixed to “zmm3-zmm0”, it will be appreciated that theregisters may be fixed to a range of other registers, .e.g.,“zmm4-zmm1”, or “zmm5-zmm2”, etc., or fixed to a set of non-contiguousregisters.

In one embodiment, the data elements are fetched from memory and storedin temporary vector registers in a manner similar to that discussedabove, prior to being stored in the destination registers.

FIGS. 3A through 3E illustrate an example of an execution of a coalescedgather instruction, which coalesces three adjacent gather instructionsaccording to certain embodiments. In this example, zmm8 holds the eightqword indices (i.e., each index is 64-bit wide) for three coalescedgather instructions. Since the destination registers (zmm0, zmm1, andzmm2) are each 512-bit wide, the size of each of the eight data elementis 8-byte wide (i.e., double precision unit). Thus, each memory readfetches a 24-byte block of memory comprised of three double-precisionvalues. In this illustration, the first, second and third destinationoperands are zmm0, zmm1, and zmm2, respectively. Thus, according to oneembodiment, the first data element of each 24-byte block is stored intothe corresponding data element of zmm0; the second data element of theblock is stored into the corresponding data element of zmm1; and thethird data element of the block is stored into the corresponding dataelement of zmm2 In these illustrations, the starting memory location ofeach block of data elements is the base address plus the value stored inthe corresponding index of the array of indices, e.g., “rax+zmm8[0].”However, for readability purposes, the Figures shall denote“rax+zmm8[0]” simply as “zmm8[0]”. This notation applies to allsubsequent Figures in the description.

Referring now to FIG. 3A, a 24-byte block of memory comprising of threedouble-precision data elements (i.e., each data element in the memory is8-byte wide) is read from memory, where the first data element of thememory block starts at memory location “rax+zmm8[0]”, the second dataelement of the memory block is eight bytes away from the startinglocation of the block, and the third data element starts at sixteenbytes away from the starting memory location of the block. The firstdata element of the memory block is stored in the first data element offirst destination register (i.e., zmm0[0]), the second data element ofthe memory block is stored in the first data element of the seconddestination register (i.e., zmm1[0]), and the third data element of thememory block is stored in the first data element of the thirddestination register (i.e., zmm2[0]). In one embodiment, the “first dataelement” of a destination register is the data element comprising of theleast significant bits (LSB) of the destination register. In anotherembodiment, the “first data element” of a destination register comprisesthe most significant bits (MSB) of the destination register.

FIG. 3B illustrates the memory read of a second 24-byte block of memory.In this illustration, the memory block starts at “rax+zmm8[1]”. Sincethe second index of zmm8 (i.e., zmm8[1]) is used to generate the memoryaddress, the contiguous data elements fetched are stored into the seconddata element of each destination register (i e, zmm0[1], zmm1[1], andzmm2[1]).

FIG. 3C illustrates the memory read of a third 24-byte block of memory,starting at the memory location “rax+zmm8[2]”. Since the third index ofzmm8 (i.e., zmm8[2]) is used to generate the memory address, thecontiguous data elements fetched are stored into the third data elementof each destination register (i.e., zmm0[2], zmm1[2], and zmm2[2]).

FIG. 3D illustrates the memory read of a fourth 24-byte block of memory,starting at the memory location “rax+zmm8[3]”. Since the fourth index ofzmm8 (i.e., zmm8[3]) is used to generate the memory address, thecontiguous data elements fetched are stored into the fourth data elementof each destination register (i.e., zmm0[3], zmm1[3], and zmm2[3]).

FIG. 3E illustrates the destination registers zmm0, zmm1, and zmm2completely packed with data elements from memory after four more 24-byteblocks of memory are read.

FIG. 4 illustrates another example of an execution of a coalesced gatherinstruction with the use of the writemask according to one embodiment.In this illustration, the base address is rax (not shown), and thevector/array of indices is zmm8 The illustration is an example ofcoalescing three adjacent gather operations, i.e., groups of three dataelements contiguously located in memory are stored into data elements ofthree destination operands (zmm2, zmm1, and zmm0), according to thewritemask k1. The writemask k1 has a hexadecimal value of 0xA3. In thisillustration, the first, second and third destination operands are zmm2,zmm1, and zmm0, respectively.

The execution of the coalesced gather instruction causes gather/scatterunit 208 to generate a first memory address and determine if read 0should be carried out. In one embodiment, the first address is the baseaddress plus the value stored in the first index of the array of indices(i.e., “rax+zmm8[0]”), which points to a memory location of the firstdata element in memory to be stored in the first data element of thefirst destination operand (zmm2[0]).

In one embodiment, gather/scatter unit 208 determines if data elementsshould be read from memory and stored in the corresponding data elementsof the destination operands according to the writemask bit values. Inthis illustration, the first (LSB) bit of the writemask, i.e., k1[0] is“1”, which in one embodiment, indicates that the first (LSB) dataelement of each destination operands should be updated. As a result, thedata element at memory location “rax+zmm8[0]” having the value “2” andthe next two contiguous data elements having the values “1” and “0”, areread from memory in a single memory access. In one embodiment, the dataelements {2, 1, 0} are stored, in a single cycle, into the zmm2[0], zmm1[0], and zmm0[0], respectively.

Similarly, gather/scatter unit 208 generates a second address pointingto the memory location “rax+zmm8[1]” and determines if read 1 should becarried out. Like k1 [0], the writemask bit k1[1] is also set to “1”,thus contiguous data elements {12, 11, 10} are fetched from memorystarting at location “rax+zmm8[1]” and stored into zmm2[1], zmm1 [1],and zmm0[1], respectively.

Gather/scatter unit 208 skips read 2 in this example because unlikek1[0] and k1[1], writemask bit k1[2] is set to “0”, which in oneembodiment, indicates that the third data element of the destinationoperands should not be updated. As a result, zmm2[2], zmm1 [2], andzmm0[2] remain unchanged, as indicated by the label “x” in FIG. 4.

Gather/scatter unit 208 performs the same logic as discussed above anddetermines that read 3, read 4, and read 6 should be skipped becausek1[3], k1[4], and k1[6] are all set to “0”. Moreover, gather/scatterunit 208 determines that read 5 should be performed because k1[5] is setto “1”, and fetches the contiguous data elements {52, 51, 50} frommemory starting at the address “rax+zmm8[5]” and stores them in zmm2[5],zmm1[5], and zmm0[5], respectively. Likewise, read 7 is performedbecause k1[7] is set to “1”, and contiguous data elements {72, 71, 70}are fetched from memory starting at location “rax+zmm8[7]” and storedinto zmm2[7], zmm1[7], and zmm0[7], respectively.

FIG. 5 is a flow diagram illustrating a method 500 of processing acoalesced gather instruction according to one embodiment. Method 500 maybe performed by processor 200 of FIG. 2. Referring to FIG. 5, at block505, a first instruction to gather contiguous data elements from memoryis decoded. In one embodiment, the first instruction includes multipleoperands, e.g., a first operand specifying a first storage location, asecond operand specifying a second storage location, and a third operandspecifying memory address. In one embodiment, the third operand includesa base address and an array of indices. The first instruction may alsoinclude a writemask. Exemplary sizes of operands have been previouslydetailed.

At block 510, in response to the first instruction, contiguous first andsecond data elements are read from memory based on the memory addressindicated by the third operand. In one embodiment, the contiguous dataelements are read from memory using a single memory access.

At block 515, the first instruction is executed to store contiguousfirst and second data elements from memory into a first entry of thefirst and second storage location, respectively. In one embodiment, thecontiguous data elements are stored into the first and second storagelocations in a single cycle. In one embodiment, the data elements arestored into temporary vector registers prior to being stored intodestination operands.

FIG. 6 is a flow diagram illustrating a method 600 for processing acoalesced gather instruction. Method 600 may be performed by processor200 of FIG. 2. In this illustration, it is assumed that some, if notall, of the operations 505-515 of FIG. 5 have been performed previously.For example, at the least, a first instruction to gather data elementshas been decoded. Referring to FIG. 6, at block 605, a first address ofa first data element in memory is generated according to a base addressand a value stored in a first index of an array of indices. In oneembodiment, the first address is the base address plus the value storedin the first index of the array of indices.

At block 610, it is determined, according to a value of the firstwritemask bit, if the data elements are to be stored into the firstentry of the first and second storage location. In one embodiment, thefirst writemask bit is the LSB bit of the writemask. When the writemaskbit does not indicate that the data elements should be stored in thefirst and second storage location, then the first entry of the first andsecond storage location are left unchanged at block 630, and theprocessing is completed. In one embodiment, a writemask bit having avalue of“0” indicates that the data elements should not be stored in thefirst and second storage location. In another embodiment, the oppositeconvention is be used.

At block 615, when the value stored in the first mask bit of thewritemask indicates that the data elements should be stored in the firstentry of the first and second storage location, then data elements areread from memory. In one embodiment, the first data element is locatedat the first address, and the second data element is contiguouslylocated next to the first data element. In one embodiment, the dataelements are read from memory in a single memory access.

At block 620, the first and second data elements are stored into thefirst and second storage location. In one embodiment, the storagelocation is an array of entries (e.g., an array of data elements), andthe first entry of the storage location is the LSB entry. In oneembodiment, the data elements are stored into the first entry of thefirst and second storage location in a single cycle. In one embodiment,the first and second data elements are stored in vector registers priorto being stored into the first and second storage location.

At block 625, the first writemask bit is cleared to indicate that thecorresponding block of data elements have been fetched and stored in thefirst and second storage location, and the process is completed.

Referring back to FIG. 1, as discussed above, gather/scatter unit 208executes gather and scatter instructions. In one embodiment, the scatterinstruction is a coalesced scatter instruction. The execution of thisinstruction by gather/scatter unit 208 stores data elements frommultiple source operands into contiguous memory locations such that thedata elements are located adjacent to each other in memory.

The source operand data elements to be loaded into memory are specifiedvia a type of SIB (scale, index, and base) addressing. The coalescedscatter instruction also includes a writemask. In some embodiments thatuse a dedicated mask register such as a “k” writemask, the sourceoperand data elements will be loaded into memory when theircorresponding writemask bit indicates that they should be (for example,in some embodiments if the bit is a “1”). If a data element'scorresponding writemask bit is not set, the corresponding data elementin memory is left unchanged.

In some embodiments with 128-bit size source registers, the instructionwill scatter up to four single-precision floating point values or twodouble-precision floating point values per source register. In someembodiments with 256-bit size source registers, the instruction willscatter up to eight single-precision floating point values or fourdouble-precision floating point values per source register. In someembodiments with 512-bit size source registers, the instruction willscatter up to sixteen single-precision floating point values or eightdouble-precision floating point values per source register.

The coalesced scatter instruction may be implemented in several formats.In one embodiment, the coalesced scatter instruction is defined asfollows:

-   -   VSCATTERQ4PD[rax+zmm9]{k1}, zmm3:zmm5:zmm6:zmm0//Format 3

where zmm3, zmm5, zmm6, and zmm0 are source vector register operands(such as a 128-, 256-, 512-bit register, etc.), k1 is a writemaskoperand (such as a 16-bit register examples of which are detailedlater), rax is the base address, and zmm9 is a vector/array of indices.In one embodiment, the base and a value stored in an index of the vectorof indices are used to generate a memory destination address where thefirst data element of the first source operand will be stored. In someembodiments, the writemask is also of a different size (8 bits, 32 bits,etc.). Additionally, in some embodiments, not all bits of the writemaskare utilized by the instruction.

In one embodiment, in the above format 3 of the coalesced scatterinstruction, the first source operand is zmm3, the second source operandis zmm5, the third source operand is zmm6, and the fourth source operandis zmm0. In another embodiment, the order of the source operands is thereverse, e.g., zmm3 is the fourth operand and zmm0 is the first operand.In one embodiment, the order of these operands explicitly indicates theorder in which data elements from each source operand will be storedinto contiguous memory. Thus, in the above format 3 example, assumingthe writemask indicates all data elements are to be updated (discussedin further details below) and assuming further that the first sourceoperand is zmm3, source operand data element zmm3 [0] is stored as thefirst data element in the contiguous block of memory starting at memorylocation “rax+zmm9[0]”. The data elements of the next three sourceoperands, i.e., zmm5[0], zmm6[0], and zmm0[0] are stored in contiguousmemory location, i.e., zmm5[0] is stored at “rax+zmm9[0]+size of(dataelement)”, zmm6[0] is stored at “rax+zmm9[0]+(2*size of(data element))”,and zmm0[0] is stored at “rax+zmm9[0]+(3*size of(data element))”. Thesecond data element of each source operand will be stored in contiguousmemory location starting at location “rax+zmm9[1]”, similar to how thefirst data elements of the source operands are stored. Thus, zmm3[1] isstored at “rax+zmm9[1]”; zmm5[1] is stored at “rax+zmm9[1]+size of(dataelement)”; zmm6[1] is stored at “rax+zmm9[1]+(2*size of(data element))”;and zmm0[1] is stored at “rax+zmm9[1]+(3*size of(data element))”. Theremaining data elements of the source operands are stored intocontiguous blocks of memory using the same logic.

VSCATTERQ4PD is the instruction's opcode. Typically, each operand isexplicitly defined in the instruction. The size of the data elements maybe defined in the “suffix” of the instruction. For instance, the suffix“PD” in the instruction VSCATTERQ4PD may indicate that the data elementis a double precision (i.e., 64 bits). In most embodiments, dataelements are either 32 or 64 bits. If the data elements are 32 bits insize, and the operands are 512 bits in size, then there are sixteen (16)data elements per operand. In some embodiments, the number of dataelements per operand implicitly indicates the number of indices that arepresent in the vector of indices (e.g., zmm9 in the above example.) Inone embodiment, the number of operands is also explicitly defined in theinstruction. For instance, in the above example, the “4” preceding the“PD” suffix may indicate that the instruction is coalescing fouradjacent scatter operations, i.e., the execution of the instructionresults in writing data elements from four source operands intocontiguous memory blocks of four data elements. In one embodiment, thesource operand data elements are written to each contiguous memory blockin a single memory access.

In another embodiment, the coalesced scatter instruction is defined asfollows:

-   -   VSCATTERQ4PD {rax+zmm9}{k1},zmm3-zmm0.//Format 4

The execution of the coalesced scatter instruction having format 4causes operations similar to those discussed above in the text relatingto format 3 to be executed. The difference between format 3 and format 4is that with format 4, the source operand registers are specified as arange of registers. In the above example of format 4, the range ofsource registers are bound by zmm3 and zmm0. Thus, implicitly, thesource registers are zmm3, zmm2, zmm1, and zmm0, where zmm2 and zmm1 areimplied by the fact that the instruction explicitly indicates dataelements from four source registers are to be packed into memory. Notethat in this embodiment, although the choice of the first sourceregister may be freely specified, it is a syntax error to specify arange of source registers that is inconsistent with the number of sourceregisters explicitly indicated by the instruction.

In another embodiment, the coalesced scatter instruction is defined asfollows:

-   -   VSCATTERQ4PD[rax+zmm9]{k1}, zmm3-zmm0.//Format 5

The execution of the coalesced scatter instruction having format 5causes operations similar to those discussed above in the text relatingto format 3 to be executed. The difference between format 3 and format 5is that with format 5, the source registers are fixed. Thus, forinstance, in the above example, the source registers are fixed to zmm3,zmm2, zmm1, and zmm0 because the instruction explicitly indicates dataelements from four source registers are to be packed into memory. Notethat in this embodiment, it is a syntax error to specify any sourceregisters other than “zmm3-zmm0” and this is specified only as an aid toreadability. Although in the above example, the registers are fixed to“zmm3-zmm0”, it will be appreciated that the registers may be fixed to arange of other registers, .e.g., “zmm4-zmm1”, or “zmm5-zmm2”, etc.

FIG. 7 illustrates an example of an execution of a coalesced scatterinstruction which includes the use of the writemask according to oneembodiment. In this illustration, the base address is rax (not shown),and the vector/array of indices is zmm8. The illustration is an exampleof coalescing three adjacent scatter operations, i.e., data elementsfrom a group of three source operands (zmm2, zmm1, and zmm0) are storedinto contiguous memory, according to the writemask k1. The writemask k1has a hexadecimal value of 0xA3. In this illustration, the first, secondand third source operands are zmm2, zmm1, and zmm0, respectively. Again,this affects the ordering of the data elements stored into the memoryblock.

The execution of the coalesced scatter instruction causes gather/scatterunit 208 to generate a first address and determine if write 0 should becarried out. In one embodiment, the first address is the base addressplus the value stored in the first index of the array of indices (i.e.,“rax+zmm8[0]”), which points to a memory location of the start of theblock of contiguous memory, where the first data element of the firstsource operand register (zmm2[0]) is to be stored.

In one embodiment, gather/scatter unit 208 determines if source operanddata elements should be stored into memory according to the writemaskbit values. In this illustration, the first (LSB) bit of the writemask,i.e., k1 [0], is “1”, which in one embodiment, indicates that the first(LSB) data element of each source operands should be packed and storedinto contiguous memory. As a result, source operand data elements {2, 1,0} of zmm2[0], zmm1 [0], and zmm0[0], respectively, are packed andstored as a block of contiguous memory, starting at the memory location“rax+zmm8[0]”.

Similarly, gather/scatter unit 208 generates a second address pointingto the memory location “rax+zmm8[1]” and determines if write 1 should becarried out. Like k1[0], the writemask bit k1[1] is also set to “1”,thus data elements {12, 11, 10} of zmm2[1], zmm1[1], and zmm0[0],respectively, are packed and stored into contiguous block of memorystarting at the memory location “rax+zmm8[1]”.

Gather/scatter unit 208 skips write 2 in this example because unlikek1[0] and k1[1], writemask bit k1[2] is set to “0”, which in oneembodiment, indicates that the third data element of the source operandsshould not be stored into memory. As result, zmm2[2], zmm1 [2], andzmm0[2] are not written to memory.

Gather/scatter unit 208 performs the same logic as discussed above anddetermines that write 3, write 4, and write 6 should be skipped becausek1[3], k1[4], and k1[6] are all set to “0”. Moreover, gather/scatterunit 208 determines that write 5 should be performed because k1[5] isset to “1”, and stores data elements {52, 51, 50} of source operandszmm2[5], zmm1 [5], and zmm0[5] into contiguous memory starting at theaddress “rax+zmm8[5]”. Likewise, write 7 is performed because k1[7] isset to “1”, and data elements {72, 71, 70} of source operands zmm2[7],zmm1 [7], and zmm0[7] are stored into contiguous memory starting atlocation “rax+zmm8 [7]”.

In the above discussion, adjacent gather/scatter instructions arecoalesced by a new ISA. It will be appreciated, however, that adjacentgather/scatter operations may also be coalesced using the current ISA bycombining them “behind the scene”. For example, the three gatherinstructions:

-   -   vgatherqpd zmm0{k1}, [rax+zmm8+0]    -   vgatherqpd zmm1{k1}, [rax+zmm8+8]    -   vgatherqpd zmm2{k1}, [rax+zmm8+16]

may be performed by the current SIMD hardware as a single coalescedgather instruction. In one embodiment, in order to be combined as acoalesced gather instruction, the three gather instructions above musthave the same operands, i.e., base, scale, index and writemask.Moreover, the instructions must have the right offsets/displacements.For example, the offset of each gather instruction must be a multiple ofthe size of the data element, so that each data element of aninstruction is contiguously located in memory next to the data elementof the preceding instruction. In one embodiment, when the above gatherinstructions are received, gather/scatter unit 208 assumes that they canbe coalesced, and issues the combined reads, and then before retiringthe instructions, checks that the instructions can be coalesced based ontheir operands. If not, the results are discarded and the instructionsare re-executed as separate gathers.

In one embodiment, the following scatter operations may be similarlycoalesced “behind the scene”:

-   -   vscatterqpd [rax+zmm8+0]{k1}, zmm0    -   vscatterqpd [rax+zmm8+8]{k1}, zmm1    -   vscatterqpd [rax+zmm8+16]{k1}, zmm2

In another embodiment, adjacent gather/scatter operations are coalescedusing the current ISA by adding a prefix to the instructions to stronglyhint that they will be fused/coalesced. For example, the gatherinstructions:

-   -   repvgatherqpd zmm0{k1}, [rax+zmm8+0]    -   repvgatherqpd zmm1 {k1}, [rax+zmm8+8]    -   vgatherqpd zmm2 {k1}, [rax+zmm8+16]

may be performed by the SIMD hardware as a single coalesced gatherinstruction. In this embodiment, the prefix “rep” assures the hardwarethat there are further gathers that can be coalesced coming along, andthat it should buffer the first few until the last gather (which has noprefix) arrives. Similarly, the following strongly hinted scatterinstructions may be coalesced:

-   -   repvscatterqpd [rax+zmm8+0]{k1}, zmm0    -   repvscatterqpd [rax+zmm8+8]{k1}, zmm1    -   vscatterqpd [rax+zmm8+16]{k1}, zmm2

FIGS. 8A-8H illustrate another embodiment of coalescing adjacent gatherinstructions using the current ISA. In this embodiment, the first gatherinstruction is sent to the gather/scatter unit 208, which will assumethat it is a first of three successive gather instructions. In thisexample, the data elements are each 8-byte wide (double precision unit),and since the destination operands zmm0, zmm1, and zmm2 are each 512-bitwide, there are eight data elements to be gathered from memory for eachdestination operand. For each data element to be gathered,gather/scatter unit 208 fetches at least eight bytes (the size of onedata element) from memory, but it will attempt to fetch up to anothersixteen bytes (two more double-precision values) without going over theend of the cache line. Gather/scatter unit 208 stores the first dataelement into the first destination operand and however many dataelements it is able to read from memory into the corresponding dataelements of the remaining destination operands. In other embodiments,gather/scatter unit 208 may store the data elements in a buffer, andcopy the data from the buffer to the destination registers as theinstructions retire. In this embodiment, gather/scatter unit 208 alsokeeps track of which data elements of the destination operands were notupdated because the data elements were on a different cache line. Inthis embodiment, gather/scatter unit 208 may also maintain a signaturecache that remembers what the current gather instruction looks like,e.g., how many data elements, their size, which base and index registerswere used, and what immediate scale and offset to the base.

Referring now to FIG. 8A, the first memory read of the first gatherinstruction is performed. In this example, the first memory block of allthree data elements can be read on the same cache line, andgather/scatter unit 208 is able to update the first data element of allthree destination operands (zmm0[0], zmm1 [0], and zmm2[0]).

FIG. 8B illustrates that the memory read by gather/scatter unit 208 forthe second data element of the destination operands does not produce theentire 3-data element block. Specifically, the third data element of theblock is on a different cache line. As a result, only the second dataelement of the first two destination operands (zmm0[1] and zmm1 [1]) areupdated with data elements from memory, and the second data element ofthe third destination operand (zmm2[1]) is not updated.

FIG. 8C illustrates that gather/scatter unit 208 is able to read theentire 3-data element block of memory during the third memory read. As aresult, the third data element of each destination operand is updated.

FIG. 8D illustrates that the fourth memory read only returns a singledouble-precision value because the second and third data element is on adifferent cache line. Thus, only the fourth data element of the firstdestination operand (zmm0[3]) is updated.

FIG. 8E illustrates that after four more memory reads, all eight dataelements of the first destination operand (zmm0) are updated. However,zmm1 [3], zmm1 [6], zmm2[1], zmm2[3], zmm2[5], and zmm2[6] have not beenupdated due to the fact that their respective data elements were ondifferent cache lines.

FIG. 8F illustrates that once the first gather instruction is completed,i.e., all data elements of zmm0 have been updated, the instruction isretired, and the next gather instruction is processed.

FIG. 8G illustrates gather/scatter unit 208 processing the second gatherinstruction by performing a memory read for the fourth data element ofthe second destination operand (zmm1 [3]). Gather/scatter unit 208skipped the memory reads for first three data elements of zmm1 becausethey were updated during the updating of zmm0, as discussed above. Notealso that in this illustration, the fourth data element of the thirddestination operand (zmm2[3]) is on the same cache line, and thus,zmm2[3] is also updated.

FIG. 8H illustrates gather/scatter unit 208 performing the last memoryread to complete the updating of zmm1, and the second gather instructionis then retired. Although not shown, gather/scatter unit 208 will updatethe remaining data elements of zmm2 using similar procedures asdiscussed above, and retire the third gather instruction.

In another embodiment, adjacent gather and scatter operations arecoalesced by transposing partial gather/scatter instructions. Asdiscussed above, to gather a 2-element structure from eight indicescurrently requires two gather instructions:

-   -   vgatherqpd zmm0 {k1}, [rax+zmm8+0]    -   vgatherqpd zmm1 {k2}, [rax+zmm8+8].

Assuming k1=k2=all “1s”, each of these instructions looks at all eightindices in zmm8 and performs a single 8-byte load. This results insixteen cache line accesses, which is twice as many as required. In thefollowing discussion, the x,y,z,w naming convention for data elementswill be used, and the shorthand “x0” means “the double-precision valueat address “rax+zmm8[0]+0”. Similarly, “y3” means “the double-precisionvalue at address rax+zmm8[3]+8”. Given this naming convention, theexecution of the above gather instructions produces the followingresults:

Zmm0 x0 x1 x2 x3 x4 x5 x6 x7 Zmm1 y0 y1 y2 y3 y4 y5 y6 y7

In one embodiment of the invention, a “partial” gather is performed thatonly uses some of the indices, but in return can load more data perindex. This can be illustrated as a pair of partial gather instructions:

-   -   vgatherp0123 qpd zmm0{k1}, [rax+zmm8+0]    -   vgatherp4567 qpd zmm1{k2}, [rax+zmm8+0].

The “0123” part of the first instruction indicates to gather/scatterunit 208 that the instruction only uses the first four indices of zmm8and the first four bits of the writemask k1. Similarly, the “4567” ofthe second instruction indicates that it only uses the second fourindices and writemask bits. Thus, the results are:

Zmm0 x0 x1 x2 x3 y0 y1 y2 y3 Zmm1 y4 y5 y6 y7 x4 x5 x6 x7

The reason for the odd ordering of the results will be explained infurther details below.

FIG. 9A illustrates the pseudo-code for the operation of vgatherp0123qpd. If Load128 faults, it is handled by the same fault handlingmechanisms as with the existing gather operations. Like the standardgather operations, it is important to clear the writemask bits as loadsare performed so that the instruction can be restarted by the operatingsystem (OS) after a fault.

FIG. 9B illustrates the pseudo-code for the operation of vgatherp4567qpd, which is similar to the pseudo-code for vgatherp0123 qpd, with thedifferences highlighted. The benefit of using these two new instructionsis that gather/scatter unit 208 is able to perform half the number ofreads (eight rather than sixteen), even though each read is twice thesize (128 bits rather than 64). Thus, this allows the sequence to runnearly twice as fast.

The above is a description of a 2-element structure. The equivalent fora 4-element structure is similar:

-   -   vgatherp01 qpd zmm0{k1}, [rax+zmm8+0]    -   vgatherp23 qpd zmm1{k2}, [rax+zmm8+0]    -   vgatherp34 qpd zmm2{k1}, [rax+zmm8+0]    -   vgatherp67 qpd zmm3{k2}, [rax+zmm8+0].

Each of the above partial gather instructions performs only two reads,but each read is 256 bits in size. The results look like this:

Zmm0 x0 x1 y0 y1 z0 z1 w0 w1 Zmm1 w2 w3 x2 x3 y2 y3 z2 z3 Zmm2 z4 z5 w4w5 x4 x5 y4 y5 Zmm3 y6 y7 z6 z7 w6 w7 x6 x7

FIGS. 10A-10D illustrate the pseudo-code for the partial gatherinstructions vgatherp01 qpd, vgatherp23 qpd, vgatherp34 qpd, andvgatherp67 qpd, respectively.

One of the advantages of the partial gather operations above is thatthey reduce the number of memory accesses. However, the disadvantage isthat the data elements written to the vector registers are not in theformat that is useful to standard vector arithmetic. In one embodiment,this formatting irregularity can be resolved by the existingshuffle/permute operations in the ISA. It is clearly possible to performthe 2-element transpose with 4 VPERMD instructions with the appropriatewritemasks and the 4-element transpose in 16 VPERMD instructions withwritemasks. Alternatively the newer VPERMI2 W instruction can permutedata from two register sources, which can be used to halve the number ofinstructions required.

Even when using these existing permutation instructions, the newsequence of gathers can outperform the existing sequences because of thesignificant reduction in memory accesses.

In one embodiment, new special-purpose instructions are used to performthe transpose in only two or four instructions, by taking advantage ofthe fact that the VPUs are constructed as four “banks” of ALU andregister file blocks, each bank handling 128 bits of the result. Thismeans that each bank can read a different source register to theadjacent bank, allowing the gather/scatter unit 208 to read parts of upto four registers while only using a single read port per bank. Thisallows a single transpose instruction to read data from all fourregisters, and then send the combined 512-bit temporary result to theshuffle unit (called “GENMUX”) to reorder the data into the correctorder.

FIGS. 11A and 11B illustrate the construction of the zmm0 and zmm1destination operands by transposing the results of the partial gathers.Referring to FIG. 11A, the GENMUX unit does not need to perform anypermutation as the data is already in the correct ordering. However, asillustrated in FIG. 11B, the Y components need to be permutated toproduce a correct ordering of data elements for zmm1. The Z and Wcomponents may be permutated in similar manner to produce zmm2 and zmm3.

In one embodiment, these operations are specified as multipleinstructions with hardcoded selection and permutation controls. Inanother embodiment, they are specified more flexibly with the controlscoming from either immediate values or from registers. Here, forsimplicity we show them as hardcoded discrete instructions.

Using these transpose instructions allows the full gather+transposeoperation to be performed very quickly. The 2-component version requirestwo gather and two transpose instructions:

-   -   vgatherp0123 qpd zmm0{k1}, [rax+zmm8+0]    -   vgatherp4567 qpd zmm1 {k1}, [rax+zmm8+0]    -   vtranspose0123 pd zmm10, zmm0, zmm1    -   vtranspose4567 pd zmm11, zmm0, zmm1.

The 4-component version requires four gather and four transposeinstructions:

-   -   vgatherp01 qpd zmm0{k1}, [rax+zmm8+0]    -   vgatherp23 qpd zmm1{k1}, [rax+zmm8+0]    -   vgatherp45 qpd zmm2{k1}, [rax+zmm8+0]    -   vgatherp67 qpd zmm3{k1}, [rax+zmm8+0]    -   vtranspose01 pd zmm10, zmm0, zmm1, zmm2, zmm3    -   vtranspose23 pd zmm11, zmm0, zmm1, zmm2, zmm3    -   vtranspose45 pd zmm12, zmm0, zmm1, zmm2, zmm3    -   vtranspose67 pd zmm13, zmm0, zmm1, zmm2, zmm3.

An instruction set, or instruction set architecture (ISA), is the partof the computer architecture related to programming, and may include thenative data types, instructions, register architecture, addressingmodes, memory architecture, interrupt and exception handling, andexternal input and output (I/O). The term instruction generally refersherein to macroinstructions—that is instructions that are provided tothe processor (or instruction converter that translates (e.g., usingstatic binary translation, dynamic binary translation including dynamiccompilation), morphs, emulates, or otherwise converts an instruction toone or more other instructions to be processed by the processor) forexecution—as opposed to micro-instructions or micro-operations(micro-ops)—that is the result of a processor's decoder decodingmacroinstructions.

The ISA is distinguished from the microarchitecture, which is theinternal design of the processor implementing the instruction set.Processors with different microarchitectures can share a commoninstruction set. For example, Intel® Pentium 4 processors, Intel® Core™processors, and processors from Advanced Micro Devices, Inc. ofSunnyvale Calif. implement nearly identical versions of the x86instruction set (with some extensions that have been added with newerversions), but have different internal designs. For example, the sameregister architecture of the ISA may be implemented in different ways indifferent microarchitectures using well-known techniques, includingdedicated physical registers, one or more dynamically allocated physicalregisters using a register renaming mechanism (e.g., the use of aRegister Alias Table (RAT), a Reorder Buffer (ROB), and a retirementregister file; the use of multiple maps and a pool of registers), etc.Unless otherwise specified, the phrases register architecture, registerfile, and register are used herein to refer to that which is visible tothe software/programmer and the manner in which instructions specifyregisters. Where a specificity is desired, the adjective logical,architectural, or software visible will be used to indicateregisters/files in the register architecture, while different adjectiveswill be used to designation registers in a given microarchitecture(e.g., physical register, reorder buffer, retirement register, registerpool).

An instruction set includes one or more instruction formats. A giveninstruction format defines various fields (number of bits, location ofbits) to specify, among other things, the operation to be performed(opcode) and the operand(s) on which that operation is to be performed.Some instruction formats are further broken down though the definitionof instruction templates (or subformats). For example, the instructiontemplates of a given instruction format may be defined to have differentsubsets of the instruction format's fields (the included fields aretypically in the same order, but at least some have different bitpositions because there are less fields included) and/or defined to havea given field interpreted differently. Thus, each instruction of an ISAis expressed using a given instruction format (and, if defined, in agiven one of the instruction templates of that instruction format) andincludes fields for specifying the operation and the operands. Forexample, an ADD instruction has a specific opcode and an instructionformat that includes an opcode field to specify that opcode and operandfields to select operands (source1/destination and source2); and anoccurrence of this ADD instruction in an instruction stream will havespecific contents in the operand fields that select specific operands.

Scientific, financial, auto-vectorized general purpose, RMS(recognition, mining, and synthesis), and visual and multimediaapplications (e.g., 2D/3D graphics, image processing, videocompression/decompression, voice recognition algorithms and audiomanipulation) often require the same operation to be performed on alarge number of data items (referred to as “data parallelism”). SingleInstruction Multiple Data (SIMD) refers to a type of instruction thatcauses a processor to perform an operation on multiple data items. SIMDtechnology is especially suited to processors that can logically dividethe bits in a register into a number of fixed-sized data elements, eachof which represents a separate value. For example, the bits in a 256-bitregister may be specified as a source operand to be operated on as fourseparate 64-bit packed data elements (quad-word (Q) size data elements),eight separate 32-bit packed data elements (double word (D) size dataelements), sixteen separate 16-bit packed data elements (word (W) sizedata elements), or thirty-two separate 8-bit data elements (byte (B)size data elements). This type of data is referred to as packed datatype or vector data type, and operands of this data type are referred toas packed data operands or vector operands. In other words, a packeddata item or vector refers to a sequence of packed data elements, and apacked data operand or a vector operand is a source or destinationoperand of a SIMD instruction (also known as a packed data instructionor a vector instruction).

By way of example, one type of SIMD instruction specifies a singlevector operation to be performed on two source vector operands in avertical fashion to generate a destination vector operand (also referredto as a result vector operand) of the same size, with the same number ofdata elements, and in the same data element order. The data elements inthe source vector operands are referred to as source data elements,while the data elements in the destination vector operand are referredto a destination or result data elements. These source vector operandsare of the same size and contain data elements of the same width, andthus they contain the same number of data elements. The source dataelements in the same bit positions in the two source vector operandsform pairs of data elements (also referred to as corresponding dataelements; that is, the data element in data element position 0 of eachsource operand correspond, the data element in data element position 1of each source operand correspond, and so on). The operation specifiedby that SIMD instruction is performed separately on each of these pairsof source data elements to generate a matching number of result dataelements, and thus each pair of source data elements has a correspondingresult data element. Since the operation is vertical and since theresult vector operand is the same size, has the same number of dataelements, and the result data elements are stored in the same dataelement order as the source vector operands, the result data elementsare in the same bit positions of the result vector operand as theircorresponding pair of source data elements in the source vectoroperands. In addition to this type of SIMD instruction, there are avariety of other types of SIMD instructions (e.g., that has only one orhas more than two source vector operands, that operate in a horizontalfashion, that generates a result vector operand that is of a differentsize, that has a different size data elements, and/or that has adifferent data element order). It should be understood that the termdestination vector operand (or destination operand) is defined as thedirect result of performing the operation specified by an instruction,including the storage of that destination operand at a location (be it aregister or at a memory address specified by that instruction) so thatit may be accessed as a source operand by another instruction (byspecification of that same location by the another instruction).

The SIMD technology, such as that employed by the Intel® Core™processors having an instruction set including x86, MMX™, Streaming SIMDExtensions (SSE), SSE2, SSE3, SSE4.1, and SSE4.2 instructions, hasenabled a significant improvement in application performance. Anadditional set of SIMD extensions, referred to the Advanced VectorExtensions (AVX) (AVX1 and AVX2) and using the Vector Extensions (VEX)coding scheme, has been, has been released and/or published (e.g., seeIntel® 64 and IA-32 Architectures Software Developers Manual, October2011; and see Intel® Advanced Vector Extensions Programming Reference,June 2011).

Embodiments of the instruction(s) described herein may be embodied indifferent formats. Additionally, exemplary systems, architectures, andpipelines are detailed below. Embodiments of the instruction(s) may beexecuted on such systems, architectures, and pipelines, but are notlimited to those detailed.

VEX encoding allows instructions to have more than two operands, andallows SIMD vector registers to be longer than 128 bits. The use of aVEX prefix provides for three-operand (or more) syntax. For example,previous two-operand instructions performed operations such as A=A+B,which overwrites a source operand. The use of a VEX prefix enablesoperands to perform nondestructive operations such as A=B+C.

FIG. 12A illustrates an AVX instruction format including a VEX prefix2102, real opcode field 2130, Mod R/M byte 2140, SIB byte 2150,displacement field 2162, and IMM8 2172. FIG. 12B illustrates whichfields from FIG. 12A make up a full opcode field 2174 and a baseoperation field 2142. FIG. 12C illustrates which fields from FIG. 12Amake up a register index field 2144.

VEX Prefix (Bytes 0-2) 2102 is encoded in a three-byte form. The firstbyte is the Format Field 2140 (VEX Byte 0, bits [7:0]), which containsan explicit C4 byte value (the unique value used for distinguishing theC4 instruction format). The second-third bytes (VEX Bytes 1-2) include anumber of bit fields providing specific capability. Specifically, REXfield 2105 (VEX Byte 1, bits [7-5]) consists of a VEX.R bit field (VEXByte 1, bit [7]-R), VEX.X bit field (VEX byte 1, bit [6]-X), and VEX.Bbit field (VEX byte 1, bit[5]-B). Other fields of the instructionsencode the lower three bits of the register indexes as is known in theart (rrr, xxx, and bbb), so that Rrrr, Xxxx, and Bbbb may be formed byadding VEX.R, VEX.X, and VEX.B. Opcode map field 2115 (VEX byte 1, bits[4:0]-mmmmm) includes content to encode an implied leading opcode byte.W Field 2164 (VEX byte 2, bit [7]-W)—is represented by the notationVEX.W, and provides different functions depending on the instruction.The role of VEX.vvvv 2120 (VEX Byte 2, bits [6:3]-vvvv) may include thefollowing: 1) VEX.vvvv encodes the first source register operand,specified in inverted (1s complement) form and is valid for instructionswith 2 or more source operands; 2) VEX.vvvv encodes the destinationregister operand, specified in is complement form for certain vectorshifts; or 3) VEX.vvvv does not encode any operand, the field isreserved and should contain 1111b. If VEX.L 2168 Size field (VEX byte 2,bit [2]-L)=0, it indicates 128 bit vector; if VEX.L=1, it indicates 256bit vector. Prefix encoding field 2125 (VEX byte 2, bits [1:0]-pp)provides additional bits for the base operation field.

Real Opcode Field 2130 (Byte 3) is also known as the opcode byte. Partof the opcode is specified in this field. MOD R/M Field 2140 (Byte 4)includes MOD field 2142 (bits [7-6]), Reg field 2144 (bits [5-3]), andR/M field 2146 (bits [2-0]). The role of Reg field 2144 may include thefollowing: encoding either the destination register operand or a sourceregister operand (the rrr of Rrrr), or be treated as an opcode extensionand not used to encode any instruction operand. The role of R/M field2146 may include the following: encoding the instruction operand thatreferences a memory address, or encoding either the destination registeroperand or a source register operand.

Scale, Index, Base (SIB)—The content of Scale field 2150 (Byte 5)includes SS2152 (bits [7-6]), which is used for memory addressgeneration. The contents of SIB.xxx 2154 (bits [5-3]) and SIB.bbb 2156(bits [2-0]) have been previously referred to with regard to theregister indexes Xxxx and Bbbb. The Displacement Field 2162 and theimmediate field (IMM8) 2172 contain address data.

A vector friendly instruction format is an instruction format that issuited for vector instructions (e.g., there are certain fields specificto vector operations). While embodiments are described in which bothvector and scalar operations are supported through the vector friendlyinstruction format, alternative embodiments use only vector operationsthe vector friendly instruction format.

FIG. 13A, FIG. 13B, and FIG. 13C are block diagrams illustrating ageneric vector friendly instruction format and instruction templatesthereof according to embodiments of the invention. FIG. 13A is a blockdiagram illustrating a generic vector friendly instruction format andclass A instruction templates thereof according to embodiments of theinvention; while FIG. 13B is a block diagram illustrating the genericvector friendly instruction format and class B instruction templatesthereof according to embodiments of the invention. Specifically, ageneric vector friendly instruction format 2200 for which are definedclass A and class B instruction templates, both of which include nomemory access 2205 instruction templates and memory access 2220instruction templates. The term generic in the context of the vectorfriendly instruction format refers to the instruction format not beingtied to any specific instruction set.

While embodiments of the invention will be described in which the vectorfriendly instruction format supports the following: a 64 byte vectoroperand length (or size) with 32 bit (4 byte) or 64 bit (8 byte) dataelement widths (or sizes) (and thus, a 64 byte vector consists of either16 doubleword-size elements or alternatively, 8 quadword-size elements);a 64 byte vector operand length (or size) with 16 bit (2 byte) or 8 bit(1 byte) data element widths (or sizes); a 32 byte vector operand length(or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit (2 byte), or 8bit (1 byte) data element widths (or sizes); and a 16 byte vectoroperand length (or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit(2 byte), or 8 bit (1 byte) data element widths (or sizes); alternativeembodiments may support more, less and/or different vector operand sizes(e.g., 256 byte vector operands) with more, less, or different dataelement widths (e.g., 128 bit (16 byte) data element widths).

The class A instruction templates in FIG. 13A include: 1) within the nomemory access 2205 instruction templates there is shown a no memoryaccess, full round control type operation 2210 instruction template anda no memory access, data transform type operation 2215 instructiontemplate; and 2) within the memory access 2220 instruction templatesthere is shown a memory access, temporal 2225 instruction template and amemory access, non-temporal 2230 instruction template. The class Binstruction templates in FIG. 13B include: 1) within the no memoryaccess 2205 instruction templates there is shown a no memory access,write mask control, partial round control type operation 2212instruction template and a no memory access, write mask control, vsizetype operation 2217 instruction template; and 2) within the memoryaccess 2220 instruction templates there is shown a memory access, writemask control 2227 instruction template.

The generic vector friendly instruction format 2200 includes thefollowing fields listed below in the order illustrated in FIG. 13A andFIG. 13B. Format field 2240—a specific value (an instruction formatidentifier value) in this field uniquely identifies the vector friendlyinstruction format, and thus occurrences of instructions in the vectorfriendly instruction format in instruction streams. As such, this fieldis optional in the sense that it is not needed for an instruction setthat has only the generic vector friendly instruction format. Baseoperation field 2242—its content distinguishes different baseoperations.

Register index field 2244—its content, directly or through addressgeneration, specifies the locations of the source and destinationoperands, be they in registers or in memory. These include a sufficientnumber of bits to select N registers from a PxQ (e.g. 32×512, 16×128,32×1024, 64×1024) register file. While in one embodiment N may be up tothree sources and one destination register, alternative embodiments maysupport more or less sources and destination registers (e.g., maysupport up to two sources where one of these sources also acts as thedestination, may support up to three sources where one of these sourcesalso acts as the destination, may support up to two sources and onedestination).

Modifier field 2246—its content distinguishes occurrences ofinstructions in the generic vector instruction format that specifymemory access from those that do not; that is, between no memory access2205 instruction templates and memory access 2220 instruction templates.Memory access operations read and/or write to the memory hierarchy (insome cases specifying the source and/or destination addresses usingvalues in registers), while non-memory access operations do not (e.g.,the source and destinations are registers). While in one embodiment thisfield also selects between three different ways to perform memoryaddress calculations, alternative embodiments may support more, less, ordifferent ways to perform memory address calculations.

Augmentation operation field 2250—its content distinguishes which one ofa variety of different operations to be performed in addition to thebase operation. This field is context specific. In one embodiment of theinvention, this field is divided into a class field 2268, an alpha field2252, and a beta field 2254. The augmentation operation field 2250allows common groups of operations to be performed in a singleinstruction rather than 2, 3, or 4 instructions. Scale field 2260—itscontent allows for the scaling of the index field's content for memoryaddress generation (e.g., for address generation that uses2^(scale)*index+base).

Displacement Field 2262A—its content is used as part of memory addressgeneration (e.g., for address generation that uses2^(scale)*index+base+displacement). Displacement Factor Field 2262B(note that the juxtaposition of displacement field 2262A directly overdisplacement factor field 2262B indicates one or the other is used)—itscontent is used as part of address generation; it specifies adisplacement factor that is to be scaled by the size of a memory access(N)—where N is the number of bytes in the memory access (e.g., foraddress generation that uses 2^(scale)*index+base+scaled displacement).Redundant low-order bits are ignored and hence, the displacement factorfield's content is multiplied by the memory operands total size (N) inorder to generate the final displacement to be used in calculating aneffective address. The value of N is determined by the processorhardware at runtime based on the full opcode field 2274 (described laterherein) and the data manipulation field 2254C. The displacement field2262A and the displacement factor field 2262B are optional in the sensethat they are not used for the no memory access 2205 instructiontemplates and/or different embodiments may implement only one or none ofthe two.

Data element width field 2264—its content distinguishes which one of anumber of data element widths is to be used (in some embodiments for allinstructions; in other embodiments for only some of the instructions).This field is optional in the sense that it is not needed if only onedata element width is supported and/or data element widths are supportedusing some aspect of the opcodes.

Write mask field 2270—its content controls, on a per data elementposition basis, whether that data element position in the destinationvector operand reflects the result of the base operation andaugmentation operation. Class A instruction templates supportmerging-writemasking, while class B instruction templates support bothmerging- and zeroing-writemasking. When merging, vector masks allow anyset of elements in the destination to be protected from updates duringthe execution of any operation (specified by the base operation and theaugmentation operation); in other one embodiment, preserving the oldvalue of each element of the destination where the corresponding maskbit has a 0. In contrast, when zeroing vector masks allow any set ofelements in the destination to be zeroed during the execution of anyoperation (specified by the base operation and the augmentationoperation); in one embodiment, an element of the destination is set to 0when the corresponding mask bit has a 0 value. A subset of thisfunctionality is the ability to control the vector length of theoperation being performed (that is, the span of elements being modified,from the first to the last one); however, it is not necessary that theelements that are modified be consecutive. Thus, the write mask field2270 allows for partial vector operations, including loads, stores,arithmetic, logical, etc. While embodiments of the invention aredescribed in which the write mask field's 2270 content selects one of anumber of write mask registers that contains the write mask to be used(and thus the write mask field's 2270 content indirectly identifies thatmasking to be performed), alternative embodiments instead or additionalallow the mask write field's 2270 content to directly specify themasking to be performed.

Immediate field 2272—its content allows for the specification of animmediate. This field is optional in the sense that is it not present inan implementation of the generic vector friendly format that does notsupport immediate and it is not present in instructions that do not usean immediate. Class field 2268—its content distinguishes betweendifferent classes of instructions. With reference to FIG. 13A and FIG.13B, the contents of this field select between class A and class Binstructions. In FIG. 13A and FIG. 13B, rounded corner squares are usedto indicate a specific value is present in a field (e.g., class A 2268Aand class B 2268B for the class field 2268 respectively in FIG. 13A andFIG. 13B).

In the case of the non-memory access 2205 instruction templates of classA, the alpha field 2252 is interpreted as an RS field 2252A, whosecontent distinguishes which one of the different augmentation operationtypes are to be performed (e.g., round 2252A.1 and data transform2252A.2 are respectively specified for the no memory access, round typeoperation 2210 and the no memory access, data transform type operation2215 instruction templates), while the beta field 2254 distinguisheswhich of the operations of the specified type is to be performed. In theno memory access 2205 instruction templates, the scale field 2260, thedisplacement field 2262A, and the displacement scale filed 2262B are notpresent.

In the no memory access full round control type operation 2210instruction template, the beta field 2254 is interpreted as a roundcontrol field 2254A, whose content(s) provide static rounding. While inthe described embodiments of the invention the round control field 2254Aincludes a suppress all floating point exceptions (SAE) field 2256 and around operation control field 2258, alternative embodiments may supportmay encode both these concepts into the same field or only have one orthe other of these concepts/fields (e.g., may have only the roundoperation control field 2258).

SAE field 2256—its content distinguishes whether or not to disable theexception event reporting; when the SAE field's 2256 content indicatessuppression is enabled, a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler.

Round operation control field 2258—its content distinguishes which oneof a group of rounding operations to perform (e.g., Round-up,Round-down, Round-towards-zero and Round-to-nearest). Thus, the roundoperation control field 2258 allows for the changing of the roundingmode on a per instruction basis. In one embodiment of the inventionwhere a processor includes a control register for specifying roundingmodes, the round operation control field's 2250 content overrides thatregister value.

In the no memory access data transform type operation 2215 instructiontemplate, the beta field 2254 is interpreted as a data transform field2254B, whose content distinguishes which one of a number of datatransforms is to be performed (e.g., no data transform, swizzle,broadcast).

In the case of a memory access 2220 instruction template of class A, thealpha field 2252 is interpreted as an eviction hint field 2252B, whosecontent distinguishes which one of the eviction hints is to be used (inFIG. 13A, temporal 2252B.1 and non-temporal 2252B.2 are respectivelyspecified for the memory access, temporal 2225 instruction template andthe memory access, non-temporal 2230 instruction template), while thebeta field 2254 is interpreted as a data manipulation field 2254C, whosecontent distinguishes which one of a number of data manipulationoperations (also known as primitives) is to be performed (e.g., nomanipulation; broadcast; up conversion of a source; and down conversionof a destination). The memory access 2220 instruction templates includethe scale field 2260, and optionally the displacement field 2262A or thedisplacement scale field 2262B.

Vector memory instructions perform vector loads from and vector storesto memory, with conversion support. As with regular vector instructions,vector memory instructions transfer data from/to memory in a dataelement-wise fashion, with the elements that are actually transferred isdictated by the contents of the vector mask that is selected as thewrite mask.

Temporal data is data likely to be reused soon enough to benefit fromcaching. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.Non-temporal data is data unlikely to be reused soon enough to benefitfrom caching in the 1st-level cache and should be given priority foreviction. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.

In the case of the instruction templates of class B, the alpha field2252 is interpreted as a write mask control (Z) field 2252C, whosecontent distinguishes whether the write masking controlled by the writemask field 2270 should be a merging or a zeroing.

In the case of the non-memory access 2205 instruction templates of classB, part of the beta field 2254 is interpreted as an RL field 2257A,whose content distinguishes which one of the different augmentationoperation types are to be performed (e.g., round 2257A.1 and vectorlength (VSIZE) 2257A.2 are respectively specified for the no memoryaccess, write mask control, partial round control type operation 2212instruction template and the no memory access, write mask control, VSIZEtype operation 2217 instruction template), while the rest of the betafield 2254 distinguishes which of the operations of the specified typeis to be performed. In the no memory access 2205 instruction templates,the scale field 2260, the displacement field 2262A, and the displacementscale filed 2262B are not present.

In the no memory access, write mask control, partial round control typeoperation 2210 instruction template, the rest of the beta field 2254 isinterpreted as a round operation field 2259A and exception eventreporting is disabled (a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler).

Round operation control field 2259A—just as round operation controlfield 2258, its content distinguishes which one of a group of roundingoperations to perform (e.g., Round-up, Round-down, Round-towards-zeroand Round-to-nearest). Thus, the round operation control field 2259Aallows for the changing of the rounding mode on a per instruction basis.In one embodiment of the invention where a processor includes a controlregister for specifying rounding modes, the round operation controlfield's 2250 content overrides that register value.

In the no memory access, write mask control, VSIZE type operation 2217instruction template, the rest of the beta field 2254 is interpreted asa vector length field 2259B, whose content distinguishes which one of anumber of data vector lengths is to be performed on (e.g., 128, 256, or512 byte).

In the case of a memory access 2220 instruction template of class B,part of the beta field 2254 is interpreted as a broadcast field 2257B,whose content distinguishes whether or not the broadcast type datamanipulation operation is to be performed, while the rest of the betafield 2254 is interpreted the vector length field 2259B. The memoryaccess 2220 instruction templates include the scale field 2260, andoptionally the displacement field 2262A or the displacement scale field2262B.

With regard to the generic vector friendly instruction format 2200, afull opcode field 2274 is shown including the format field 2240, thebase operation field 2242, and the data element width field 2264. Whileone embodiment is shown where the full opcode field 2274 includes all ofthese fields, the full opcode field 2274 includes less than all of thesefields in embodiments that do not support all of them. The full opcodefield 2274 provides the operation code (opcode).

The augmentation operation field 2250, the data element width field2264, and the write mask field 2270 allow these features to be specifiedon a per instruction basis in the generic vector friendly instructionformat. The combination of write mask field and data element width fieldcreate typed instructions in that they allow the mask to be appliedbased on different data element widths.

The various instruction templates found within class A and class B arebeneficial in different situations. In some embodiments of theinvention, different processors or different cores within a processormay support only class A, only class B, or both classes. For instance, ahigh performance general purpose out-of-order core intended forgeneral-purpose computing may support only class B, a core intendedprimarily for graphics and/or scientific (throughput) computing maysupport only class A, and a core intended for both may support both (ofcourse, a core that has some mix of templates and instructions from bothclasses but not all templates and instructions from both classes iswithin the purview of the invention). Also, a single processor mayinclude multiple cores, all of which support the same class or in whichdifferent cores support different class. For instance, in a processorwith separate graphics and general purpose cores, one of the graphicscores intended primarily for graphics and/or scientific computing maysupport only class A, while one or more of the general purpose cores maybe high performance general purpose cores with out of order executionand register renaming intended for general-purpose computing thatsupport only class B. Another processor that does not have a separategraphics core, may include one more general purpose in-order orout-of-order cores that support both class A and class B. Of course,features from one class may also be implemented in the other class indifferent embodiments of the invention. Programs written in a high levellanguage would be put (e.g., just in time compiled or staticallycompiled) into an variety of different executable forms, including: 1) aform having only instructions of the class(es) supported by the targetprocessor for execution; or 2) a form having alternative routineswritten using different combinations of the instructions of all classesand having control flow code that selects the routines to execute basedon the instructions supported by the processor which is currentlyexecuting the code.

FIG. 14 is a block diagram illustrating a specific vector friendlyinstruction format according to embodiments of the invention. FIG. 14shows a specific vector friendly instruction format 2300 that isspecific in the sense that it specifies the location, size,interpretation, and order of the fields, as well as values for some ofthose fields. The specific vector friendly instruction format 2300 maybe used to extend the x86 instruction set, and thus some of the fieldsare similar or the same as those used in the existing x86 instructionset and extension thereof (e.g., AVX). This format remains consistentwith the prefix encoding field, real opcode byte field, MOD R/M field,SIB field, displacement field, and immediate fields of the existing x86instruction set with extensions. The fields from FIG. 13 into which thefields from FIG. 14 map are illustrated.

It should be understood that, although embodiments of the invention aredescribed with reference to the specific vector friendly instructionformat 2300 in the context of the generic vector friendly instructionformat 2200 for illustrative purposes, the invention is not limited tothe specific vector friendly instruction format 2300 except whereclaimed. For example, the generic vector friendly instruction format2200 contemplates a variety of possible sizes for the various fields,while the specific vector friendly instruction format 2300 is shown ashaving fields of specific sizes. By way of specific example, while thedata element width field 2264 is illustrated as a one bit field in thespecific vector friendly instruction format 2300, the invention is notso limited (that is, the generic vector friendly instruction format 2200contemplates other sizes of the data element width field 2264).

The generic vector friendly instruction format 2200 includes thefollowing fields listed below in the order illustrated in FIG. 14A. EVEXPrefix (Bytes 0-3) 2302—is encoded in a four-byte form. Format Field2240 (EVEX Byte 0, bits [7:0])—the first byte (EVEX Byte 0) is theformat field 2240 and it contains 0x62 (the unique value used fordistinguishing the vector friendly instruction format in one embodimentof the invention). The second-fourth bytes (EVEX Bytes 1-3) include anumber of bit fields providing specific capability.

REX field 2305 (EVEX Byte 1, bits [7-5])—consists of a EVEX.R bit field(EVEX Byte 1, bit [7]-R), EVEX.X bit field (EVEX byte 1, bit [6]-X), and2257BEX byte 1, bit[5]-B). The EVEX.R, EVEX.X, and EVEX.B bit fieldsprovide the same functionality as the corresponding VEX bit fields, andare encoded using 1s complement form, i.e. ZMM0 is encoded as 1111B,ZMM15 is encoded as 0000B. Other fields of the instructions encode thelower three bits of the register indexes as is known in the art (rrr,xxx, and bbb), so that Rrrr, Xxxx, and Bbbb may be formed by addingEVEX.R, EVEX.X, and EVEX.B.

REX′ field 2210—this is the first part of the REX′ field 2210 and is theEVEX.R′ bit field (EVEX Byte 1, bit [4]-R′) that is used to encodeeither the upper 16 or lower 16 of the extended 32 register set. In oneembodiment of the invention, this bit, along with others as indicatedbelow, is stored in bit inverted format to distinguish (in thewell-known x86 32-bit mode) from the BOUND instruction, whose realopcode byte is 62, but does not accept in the MOD R/M field (describedbelow) the value of 11 in the MOD field; alternative embodiments of theinvention do not store this and the other indicated bits below in theinverted format. A value of 1 is used to encode the lower 16 registers.In other words, R′Rrrr is formed by combining EVEX.R′, EVEX.R, and theother RRR from other fields.

Opcode map field 2315 (EVEX byte 1, bits [3:0]-mmmm)—its content encodesan implied leading opcode byte (0F, 0F 38, or 0F 3). Data element widthfield 2264 (EVEX byte 2, bit [7]-W)—is represented by the notationEVEX.W. EVEX.W is used to define the granularity (size) of the datatype(either 32-bit data elements or 64-bit data elements). EVEX.vvvv 2320(EVEX Byte 2, bits [6:3]-vvvv)—the role of EVEX.vvvv may include thefollowing: 1) EVEX.vvvv encodes the first source register operand,specified in inverted (1s complement) form and is valid for instructionswith 2 or more source operands; 2) EVEX.vvvv encodes the destinationregister operand, specified in is complement form for certain vectorshifts; or 3) EVEX.vvvv does not encode any operand, the field isreserved and should contain 1111b. Thus, EVEX.vvvv field 2320 encodesthe 4 low-order bits of the first source register specifier stored ininverted (1s complement) form. Depending on the instruction, an extradifferent EVEX bit field is used to extend the specifier size to 32registers. EVEX.0 2268 Class field (EVEX byte 2, bit [2]-U)—If EVEX.0=0,it indicates class A or EVEX.U0; if EVEX.0=1, it indicates class B orEVEX.U1.

Prefix encoding field 2325 (EVEX byte 2, bits [1:0]-pp)—providesadditional bits for the base operation field. In addition to providingsupport for the legacy SSE instructions in the EVEX prefix format, thisalso has the benefit of compacting the SIMD prefix (rather thanrequiring a byte to express the SIMD prefix, the EVEX prefix requiresonly 2 bits). In one embodiment, to support legacy SSE instructions thatuse a SIMD prefix (66H, F2H, F3H) in both the legacy format and in theEVEX prefix format, these legacy SIMD prefixes are encoded into the SIMDprefix encoding field; and at runtime are expanded into the legacy SIMDprefix prior to being provided to the decoder's PLA (so the PLA canexecute both the legacy and EVEX format of these legacy instructionswithout modification). Although newer instructions could use the EVEXprefix encoding field's content directly as an opcode extension, certainembodiments expand in a similar fashion for consistency but allow fordifferent meanings to be specified by these legacy SIMD prefixes. Analternative embodiment may redesign the PLA to support the 2 bit SIMDprefix encodings, and thus not require the expansion.

Alpha field 2252 (EVEX byte 3, bit [7]-EH; also known as EVEX.EH,EVEX.rs, EVEX.RL, EVEX.write mask control, and EVEX.N; also illustratedwith a)—as previously described, this field is context specific. Betafield 2254 (EVEX byte 3, bits [6:4]-SSS, also known as EVEX.s₂₋₀,EVEX.r₂₋₀, EVEX.rr1, EVEX.LL0, EVEX.LLB; also illustrated with βββ)—aspreviously described, this field is context specific.

REX′ field 2210—this is the remainder of the REX′ field and is theEVEX.V′ bit field (EVEX Byte 3, bit [3]-V′) that may be used to encodeeither the upper 16 or lower 16 of the extended 32 register set. Thisbit is stored in bit inverted format. A value of 1 is used to encode thelower 16 registers. In other words, V′VVVV is formed by combiningEVEX.V′, EVEX.vvvv.

Write mask field 2270 (EVEX byte 3, bits [2:0]-kkk)—its contentspecifies the index of a register in the write mask registers aspreviously described. In one embodiment of the invention, the specificvalue EVEX.kkk=000 has a special behavior implying no write mask is usedfor the particular instruction (this may be implemented in a variety ofways including the use of a write mask hardwired to all ones or hardwarethat bypasses the masking hardware).

Real Opcode Field 2330 (Byte 4) is also known as the opcode byte. Partof the opcode is specified in this field. MOD R/M Field 2340 (Byte 5)includes MOD field 2342, Reg field 2344, and R/M field 2346. Aspreviously described, the MOD field's 2342 content distinguishes betweenmemory access and non-memory access operations. The role of Reg field2344 can be summarized to two situations: encoding either thedestination register operand or a source register operand, or be treatedas an opcode extension and not used to encode any instruction operand.The role of R/M field 2346 may include the following: encoding theinstruction operand that references a memory address, or encoding eitherthe destination register operand or a source register operand.

Scale, Index, Base (SIB) Byte (Byte 6)—As previously described, thescale field's 2250 content is used for memory address generation.SIB.xxx 2354 and SIB.bbb 2356—the contents of these fields have beenpreviously referred to with regard to the register indexes Xxxx andBbbb. Displacement field 2262A (Bytes 7-10)—when MOD field 2342 contains10, bytes 7-10 are the displacement field 2262A, and it works the sameas the legacy 32-bit displacement (disp32) and works at bytegranularity.

Displacement factor field 2262B (Byte 7)—when MOD field 2342 contains01, byte 7 is the displacement factor field 2262B. The location of thisfield is that same as that of the legacy x86 instruction set 8-bitdisplacement (disp8), which works at byte granularity. Since disp8 issign extended, it can only address between −128 and 127 bytes offsets;in terms of 64 byte cache lines, disp8 uses 8 bits that can be set toonly four really useful values −128, −64, 0, and 64; since a greaterrange is often needed, disp32 is used; however, disp32 requires 4 bytes.In contrast to disp8 and disp32, the displacement factor field 2262B isa reinterpretation of disp8; when using displacement factor field 2262B,the actual displacement is determined by the content of the displacementfactor field multiplied by the size of the memory operand access (N).This type of displacement is referred to as disp8*N. This reduces theaverage instruction length (a single byte of used for the displacementbut with a much greater range). Such compressed displacement is based onthe assumption that the effective displacement is multiple of thegranularity of the memory access, and hence, the redundant low-orderbits of the address offset do not need to be encoded. In other words,the displacement factor field 2262B substitutes the legacy x86instruction set 8-bit displacement. Thus, the displacement factor field2262B is encoded the same way as an x86 instruction set 8-bitdisplacement (so no changes in the ModRM/SIB encoding rules) with theonly exception that disp8 is overloaded to disp8*N. In other words,there are no changes in the encoding rules or encoding lengths but onlyin the interpretation of the displacement value by hardware (which needsto scale the displacement by the size of the memory operand to obtain abyte-wise address offset) Immediate field 2272 operates as previouslydescribed.

FIG. 14B is a block diagram illustrating the fields of the specificvector friendly instruction format 2300 that make up the full opcodefield 2274 according to one embodiment of the invention. Specifically,the full opcode field 2274 includes the format field 2240, the baseoperation field 2242, and the data element width (W) field 2264. Thebase operation field 2242 includes the prefix encoding field 2325, theopcode map field 2315, and the real opcode field 2330.

FIG. 14C is a block diagram illustrating the fields of the specificvector friendly instruction format 2300 that make up the register indexfield 2244 according to one embodiment of the invention. Specifically,the register index field 2244 includes the REX field 2305, the REX′field 2310, the MODR/M.reg field 2344, the MODR/M.r/m field 2346, theVVVV field 2320, xxx field 2354, and the bbb field 2356.

FIG. 14D is a block diagram illustrating the fields of the specificvector friendly instruction format 2300 that make up the augmentationoperation field 2250 according to one embodiment of the invention. Whenthe class (U) field 2268 contains 0, it signifies EVEX.U0 (class A2268A); when it contains 1, it signifies EVEX.U1 (class B 2268B). WhenU=0 and the MOD field 2342 contains 11 (signifying a no memory accessoperation), the alpha field 2252 (EVEX byte 3, bit [7]-EH) isinterpreted as the rs field 2252A. When the rs field 2252A contains a 1(round 2252A.1), the beta field 2254 (EVEX byte 3, bits [6:4]-SSS) isinterpreted as the round control field 2254A. The round control field2254A includes a one bit SAE field 2256 and a two bit round operationfield 2258. When the rs field 2252A contains a 0 (data transform2252A.2), the beta field 2254 (EVEX byte 3, bits [6:4]-SSS) isinterpreted as a three bit data transform field 2254B. When U=0 and theMOD field 2342 contains 00, 01, or 10 (signifying a memory accessoperation), the alpha field 2252 (EVEX byte 3, bit [7]-EH) isinterpreted as the eviction hint (EH) field 2252B and the beta field2254 (EVEX byte 3, bits [6:4]-SSS) is interpreted as a three bit datamanipulation field 2254C.

When U=1, the alpha field 2252 (EVEX byte 3, bit [7]-EH) is interpretedas the write mask control (Z) field 2252C. When U=1 and the MOD field2342 contains 11 (signifying a no memory access operation), part of thebeta field 2254 (EVEX byte 3, bit [4]-S₀) is interpreted as the RL field2257A; when it contains a 1 (round 2257A.1) the rest of the beta field2254 (EVEX byte 3, bit [6-5]-S₂₋₁) is interpreted as the round operationfield 2259A, while when the RL field 2257A contains a 0 (VSIZE 2257.A2)the rest of the beta field 2254 (EVEX byte 3, bit [6-5]-S₂₋₁) isinterpreted as the vector length field 2259B (EVEX byte 3, bit[6-5]-L₁₋₀). When U=1 and the MOD field 2342 contains 00, 01, or 10(signifying a memory access operation), the beta field 2254 (EVEX byte3, bits [6:4]-SSS) is interpreted as the vector length field 2259B (EVEXbyte 3, bit [6-5]-L₁₋₀) and the broadcast field 2257B (EVEX byte 3, bit[4]-B).

FIG. 15 is a block diagram of a register architecture 2400 according toone embodiment of the invention. In the embodiment illustrated, thereare 32 vector registers 2410 that are 512 bits wide; these registers arereferenced as zmm0 through zmm31. The lower order 256 bits of the lower16 zmm registers are overlaid on registers ymm0-16. The lower order 128bits of the lower 16 zmm registers (the lower order 128 bits of the ymmregisters) are overlaid on registers xmm0-15. The specific vectorfriendly instruction format 2300 operates on these overlaid registerfile as illustrated in the below tables.

Adjustable Vector Length Class Operations Registers Instruction A (FIG.13A; 2210, 2215, zmm registers Templates that U = 0) 2225, 2230 (thevector do not include length is 64 byte) the vector length B (FIG. 13B;2212 zmm registers field 2259B U = 1) (the vector length is 64 byte)Instruction B (FIG. 13B; 2217, 2227 zmm, ymm, or Templates that U = 1)xmm registers do include the (the vector vector length length is 64byte, field 2259B 32 byte, or 16 byte) depending on the vector lengthfield 2259B

In other words, the vector length field 2259B selects between a maximumlength and one or more other shorter lengths, where each such shorterlength is half the length of the preceding length; and instructionstemplates without the vector length field 2259B operate on the maximumvector length. Further, in one embodiment, the class B instructiontemplates of the specific vector friendly instruction format 2300operate on packed or scalar single/double-precision floating point dataand packed or scalar integer data. Scalar operations are operationsperformed on the lowest order data element position in an zmm/ymm/xmmregister; the higher order data element positions are either left thesame as they were prior to the instruction or zeroed depending on theembodiment.

Write mask registers 2415—in the embodiment illustrated, there are 8write mask registers (k0 through k7), each 64 bits in size. In analternate embodiment, the write mask registers 2415 are 16 bits in size.As previously described, in one embodiment of the invention, the vectormask register k0 cannot be used as a write mask; when the encoding thatwould normally indicate k0 is used for a write mask, it selects ahardwired write mask of 0xFFFF, effectively disabling write masking forthat instruction.

General-purpose registers 2425—in the embodiment illustrated, there aresixteen 64-bit general-purpose registers that are used along with theexisting x86 addressing modes to address memory operands. Theseregisters are referenced by the names RAX, RBX, RCX, RDX, RBP, RSI, RDI,RSP, and R8 through R15.

Scalar floating point stack register file (x87 stack) 2445, on which isaliased the MMX packed integer flat register file 2450—in the embodimentillustrated, the x87 stack is an eight-element stack used to performscalar floating-point operations on 32/64/80-bit floating point datausing the x87 instruction set extension; while the MMX registers areused to perform operations on 64-bit packed integer data, as well as tohold operands for some operations performed between the MMX and XMMregisters.

Alternative embodiments of the invention may use wider or narrowerregisters. Additionally, alternative embodiments of the invention mayuse more, less, or different register files and registers.

Processor cores may be implemented in different ways, for differentpurposes, and in different processors. For instance, implementations ofsuch cores may include: 1) a general purpose in-order core intended forgeneral-purpose computing; 2) a high performance general purposeout-of-order core intended for general-purpose computing; 3) a specialpurpose core intended primarily for graphics and/or scientific(throughput) computing. Implementations of different processors mayinclude: 1) a CPU including one or more general purpose in-order coresintended for general-purpose computing and/or one or more generalpurpose out-of-order cores intended for general-purpose computing; and2) a coprocessor including one or more special purpose cores intendedprimarily for graphics and/or scientific (throughput). Such differentprocessors lead to different computer system architectures, which mayinclude: 1) the coprocessor on a separate chip from the CPU; 2) thecoprocessor on a separate die in the same package as a CPU; 3) thecoprocessor on the same die as a CPU (in which case, such a coprocessoris sometimes referred to as special purpose logic, such as integratedgraphics and/or scientific (throughput) logic, or as special purposecores); and 4) a system on a chip that may include on the same die thedescribed CPU (sometimes referred to as the application core(s) orapplication processor(s)), the above described coprocessor, andadditional functionality. Exemplary core architectures are describednext, followed by descriptions of processors and computer architectures.

FIG. 16A is a block diagram illustrating both anin-order pipeline and aregister renaming, out-of-order issue/execution pipeline according toembodiments of the invention. FIG. 16B is a block diagram illustratingboth an embodiment of an in-order architecture core and an registerrenaming, out-of-order issue/execution architecture core to be includedin a processor according to embodiments of the invention. The solidlined boxes illustrate the in-order pipeline and in-order core, whilethe optional addition of the dashed lined boxes illustrates the registerrenaming, out-of-order issue/execution pipeline and core. Given that thein-order aspect is a subset of the out-of-order aspect, the out-of-orderaspect will be described.

In FIG. 16A, a processor pipeline 2500 includes a fetch stage 2502, alength decode stage 2504, a decode stage 2506, an allocation stage 2508,a renaming stage 2510, a scheduling (also known as a dispatch or issue)stage 2512, a register read/memory read stage 2514, an execute stage2516, a write back/memory write stage 2518, an exception handling stage2522, and a commit stage 2524.

FIG. 16B shows processor core 2590 including a front end unit 2530coupled to an execution engine unit 2550, and both are coupled to amemory unit 2570. The core 2590 may be a reduced instruction setcomputing (RISC) core, a complex instruction set computing (CISC) core,a very long instruction word (VLIW) core, or a hybrid or alternativecore type. As yet another option, the core 2590 may be a special-purposecore, such as, for example, a network or communication core, compressionengine, coprocessor core, general purpose computing graphics processingunit (GPGPU) core, graphics core, or the like.

The front end unit 2530 includes a branch prediction unit 2532 coupledto an instruction cache unit 2534, which is coupled to an instructiontranslation lookaside buffer (TLB) 2536, which is coupled to aninstruction fetch unit 2538, which is coupled to a decode unit 2540. Thedecode unit 2540 (or decoder) may decode instructions, and generate asan output one or more micro-operations, micro-code entry points,microinstructions, other instructions, or other control signals, whichare decoded from, or which otherwise reflect, or are derived from, theoriginal instructions. The decode unit 2540 may be implemented usingvarious different mechanisms. Examples of suitable mechanisms include,but are not limited to, look-up tables, hardware implementations,programmable logic arrays (PLAs), microcode read only memories (ROMs),etc. In one embodiment, the core 2590 includes a microcode ROM or othermedium that stores microcode for certain macroinstructions (e.g., indecode unit 2540 or otherwise within the front end unit 2530). Thedecode unit 2540 is coupled to a rename/allocator unit 2552 in theexecution engine unit 2550.

The execution engine unit 2550 includes the rename/allocator unit 2552coupled to a retirement unit 2554 and a set of one or more schedulerunit(s) 2556. The scheduler unit(s) 2556 represents any number ofdifferent schedulers, including reservations stations, centralinstruction window, etc. The scheduler unit(s) 2556 is coupled to thephysical register file(s) unit(s) 2558. Each of the physical registerfile(s) units 2558 represents one or more physical register files,different ones of which store one or more different data types, such asscalar integer, scalar floating point, packed integer, packed floatingpoint, vector integer, vector floating point, status (e.g., aninstruction pointer that is the address of the next instruction to beexecuted), etc.

In one embodiment, the physical register file(s) unit 2558 comprises avector registers unit, a write mask registers unit, and a scalarregisters unit. These register units may provide architectural vectorregisters, vector mask registers, and general purpose registers. Thephysical register file(s) unit(s) 2558 is overlapped by the retirementunit 2554 to illustrate various ways in which register renaming andout-of-order execution may be implemented (e.g., using a reorderbuffer(s) and a retirement register file(s); using a future file(s), ahistory buffer(s), and a retirement register file(s); using a registermaps and a pool of registers; etc.). The retirement unit 2554 and thephysical register file(s) unit(s) 2558 are coupled to the executioncluster(s) 2560.

The execution cluster(s) 2560 includes a set of one or more executionunits 2562 and a set of one or more memory access units 2564. Theexecution units 2562 may perform various operations (e.g., shifts,addition, subtraction, multiplication) and on various types of data(e.g., scalar floating point, packed integer, packed floating point,vector integer, vector floating point). While some embodiments mayinclude a number of execution units dedicated to specific functions orsets of functions, other embodiments may include only one execution unitor multiple execution units that all perform all functions.

The scheduler unit(s) 2556, physical register file(s) unit(s) 2558, andexecution cluster(s) 2560 are shown as being possibly plural becausecertain embodiments create separate pipelines for certain types ofdata/operations (e.g., a scalar integer pipeline, a scalar floatingpoint/packed integer/packed floating point/vector integer/vectorfloating point pipeline, and/or a memory access pipeline that each havetheir own scheduler unit, physical register file(s) unit, and/orexecution cluster—and in the case of a separate memory access pipeline,certain embodiments are implemented in which only the execution clusterof this pipeline has the memory access unit(s) 2564). It should also beunderstood that where separate pipelines are used, one or more of thesepipelines may be out-of-order issue/execution and the rest in-order.

The set of memory access units 2564 is coupled to the memory unit 2570,which includes a data TLB unit 2572 coupled to a data cache unit 2574coupled to a level 2 (L2) cache unit 2576. In one embodiment, the memoryaccess units 2564 may include a load unit, a store address unit, and astore data unit, each of which is coupled to the data TLB unit 2572 inthe memory unit 2570. The instruction cache unit 2534 is further coupledto a level 2 (L2) cache unit 2576 in the memory unit 2570. The L2 cacheunit 2576 is coupled to one or more other levels of cache and eventuallyto a main memory.

By way of example, the register renaming, out-of-order issue/executioncore architecture may implement the pipeline 2500 as follows: 1) theinstruction fetch 2538 performs the fetch and length decoding stages2502 and 2504; 2) the decode unit 2540 performs the decode stage 2506;3) the rename/allocator unit 2552 performs the allocation stage 2508 andrenaming stage 2510; 4) the scheduler unit(s) 2556 performs the schedulestage 2512; 5) the physical register file(s) unit(s) 2558 and the memoryunit 2570 perform the register read/memory read stage 2514; theexecution cluster 2560 perform the execute stage 2516; 6) the memoryunit 2570 and the physical register file(s) unit(s) 2558 perform thewrite back/memory write stage 2518; 7) various units may be involved inthe exception handling stage 2522; and 8) the retirement unit 2554 andthe physical register file(s) unit(s) 2558 perform the commit stage2524.

The core 2590 may support one or more instructions sets (e.g., the x86instruction set (with some extensions that have been added with newerversions); the MIPS instruction set of MIPS Technologies of Sunnyvale,Calif.; the ARM instruction set (with optional additional extensionssuch as NEON) of ARM Holdings of Sunnyvale, Calif.), including theinstruction(s) described herein. In one embodiment, the core 2590includes logic to support a packed data instruction set extension (e.g.,AVX1, AVX2, and/or some form of the generic vector friendly instructionformat (U=0 and/or U=1) previously described), thereby allowing theoperations used by many multimedia applications to be performed usingpacked data.

It should be understood that the core may support multithreading(executing two or more parallel sets of operations or threads), and maydo so in a variety of ways including time sliced multithreading,simultaneous multithreading (where a single physical core provides alogical core for each of the threads that physical core issimultaneously multithreading), or a combination thereof (e.g., timesliced fetching and decoding and simultaneous multithreading thereaftersuch as in the Intel® Hyperthreading technology).

While register renaming is described in the context of out-of-orderexecution, it should be understood that register renaming may be used inan in-order architecture. While the illustrated embodiment of theprocessor also includes separate instruction and data cache units2534/2574 and a shared L2 cache unit 2576, alternative embodiments mayhave a single internal cache for both instructions and data, such as,for example, a Level 1 (L1) internal cache, or multiple levels ofinternal cache. In some embodiments, the system may include acombination of an internal cache and an external cache that is externalto the core and/or the processor. Alternatively, all of the cache may beexternal to the core and/or the processor.

FIG. 17A and FIG. 17B illustrate a block diagram of a more specificin-order core architecture, which core would be one of several logicblocks (including other cores of the same type and/or different types)in a chip. The logic blocks communicate through a high-bandwidthinterconnect network (e.g., a ring network) with some fixed functionlogic, memory I/O interfaces, and other necessary I/O logic, dependingon the application.

FIG. 17A is a block diagram of a single processor core, along with itsconnection to the on-die interconnect network 2602 and with its localsubset of the Level 2 (L2) cache 2604, according to embodiments of theinvention. In one embodiment, an instruction decoder 2600 supports thex86 instruction set with a packed data instruction set extension. An L1cache 2606 allows low-latency accesses to cache memory into the scalarand vector units. While in one embodiment (to simplify the design), ascalar unit 2608 and a vector unit 2610 use separate register sets(respectively, scalar registers 2612 and vector registers 2614) and datatransferred between them is written to memory and then read back in froma level 1 (L1) cache 2606, alternative embodiments of the invention mayuse a different approach (e.g., use a single register set or include acommunication path that allow data to be transferred between the tworegister files without being written and read back).

The local subset of the L2 cache 2604 is part of a global L2 cache thatis divided into separate local subsets, one per processor core. Eachprocessor core has a direct access path to its own local subset of theL2 cache 2604. Data read by a processor core is stored in its L2 cachesubset 2604 and can be accessed quickly, in parallel with otherprocessor cores accessing their own local L2 cache subsets. Data writtenby a processor core is stored in its own L2 cache subset 2604 and isflushed from other subsets, if necessary. The ring network ensurescoherency for shared data. The ring network is bi-directional to allowagents such as processor cores, L2 caches and other logic blocks tocommunicate with each other within the chip. Each ring data-path is1012-bits wide per direction.

FIG. 17B is an expanded view of part of the processor core in FIG. 17Aaccording to embodiments of the invention. FIG. 17B includes an L1 datacache 2606A part of the L1 cache 2604, as well as more detail regardingthe vector unit 2610 and the vector registers 2614. Specifically, thevector unit 2610 is a 16-wide vector processing unit (VPU) (see the16-wide ALU 2628), which executes one or more of integer,single-precision float, and double-precision float instructions. The VPUsupports swizzling the register inputs with swizzle unit 2620, numericconversion with numeric convert units 2622A-B, and replication withreplication unit 2624 on the memory input. Write mask registers 2626allow predicating resulting vector writes.

FIG. 18 is a block diagram of a processor 2700 that may have more thanone core, may have an integrated memory controller, and may haveintegrated graphics according to embodiments of the invention. The solidlined boxes in FIG. 18 illustrate a processor 2700 with a single core2702A, a system agent 2710, a set of one or more bus controller units2716, while the optional addition of the dashed lined boxes illustratesan alternative processor 2700 with multiple cores 2702A-N, a set of oneor more integrated memory controller unit(s) 2714 in the system agentunit 2710, and special purpose logic 2708.

Thus, different implementations of the processor 2700 may include: 1) aCPU with the special purpose logic 2708 being integrated graphics and/orscientific (throughput) logic (which may include one or more cores), andthe cores 2702A-N being one or more general purpose cores (e.g., generalpurpose in-order cores, general purpose out-of-order cores, acombination of the two); 2) a coprocessor with the cores 2702A-N being alarge number of special purpose cores intended primarily for graphicsand/or scientific (throughput); and 3) a coprocessor with the cores2702A-N being a large number of general purpose in-order cores. Thus,the processor 2700 may be a general-purpose processor, coprocessor orspecial-purpose processor, such as, for example, a network orcommunication processor, compression engine, graphics processor, GPGPU(general purpose graphics processing unit), a high-throughput manyintegrated core (MIC) coprocessor (including 30 or more cores), embeddedprocessor, or the like. The processor may be implemented on one or morechips. The processor 2700 may be a part of and/or may be implemented onone or more substrates using any of a number of process technologies,such as, for example, BiCMOS, CMOS, or NMOS.

The memory hierarchy includes one or more levels of cache within thecores, a set or one or more shared cache units 2706, and external memory(not shown) coupled to the set of integrated memory controller units2714. The set of shared cache units 2706 may include one or moremid-level caches, such as level 2 (L2), level 3 (L3), level 4 (L4), orother levels of cache, a last level cache (LLC), and/or combinationsthereof. While in one embodiment a ring based interconnect unit 2712interconnects the integrated graphics logic 2708, the set of sharedcache units 2706, and the system agent unit 2710/integrated memorycontroller unit(s) 2714, alternative embodiments may use any number ofwell-known techniques for interconnecting such units. In one embodiment,coherency is maintained between one or more cache units 2706 and cores2702-A-N.

In some embodiments, one or more of the cores 2702A-N are capable ofmultithreading. The system agent 2710 includes those componentscoordinating and operating cores 2702A-N. The system agent unit 2710 mayinclude for example a power control unit (PCU) and a display unit. ThePCU may be or include logic and components needed for regulating thepower state of the cores 2702A-N and the integrated graphics logic 2708.The display unit is for driving one or more externally connecteddisplays.

The cores 2702A-N may be homogenous or heterogeneous in terms ofarchitecture instruction set; that is, two or more of the cores 2702A-Nmay be capable of execution the same instruction set, while others maybe capable of executing only a subset of that instruction set or adifferent instruction set.

FIG. 19 to FIG. 23 are block diagrams of computer architectures. Othersystem designs and configurations known in the arts for laptops,desktops, handheld PCs, personal digital assistants, engineeringworkstations, servers, network devices, network hubs, switches, embeddedprocessors, digital signal processors (DSPs), graphics devices, videogame devices, set-top boxes, micro controllers, cell phones, portablemedia players, hand held devices, and various other electronic devices,are also suitable. In general, a huge variety of systems or electronicdevices capable of incorporating a processor and/or other executionlogic as disclosed herein are generally suitable.

Referring now to FIG. 19, shown is a block diagram of a system 2800 inaccordance with one embodiment of the present invention. The system 2800may include one or more processors 2810, 2815, which are coupled to acontroller hub 2820. In one embodiment the controller hub 2820 includesa graphics memory controller hub (GMCH) 2890 and an Input/Output Hub(IOH) 2850 (which may be on separate chips); the GMCH 2890 includesmemory and graphics controllers to which are coupled memory 2840 and acoprocessor 2845; the IOH 2850 is couples input/output (I/O) devices2860 to the GMCH 2890. Alternatively, one or both of the memory andgraphics controllers are integrated within the processor (as describedherein), the memory 2840 and the coprocessor 2845 are coupled directlyto the processor 2810, and the controller hub 2820 in a single chip withthe IOH 2850.

The optional nature of additional processors 2815 is denoted in FIG. 19with broken lines. Each processor 2810, 2815 may include one or more ofthe processing cores described herein and may be some version of theprocessor 2700.

The memory 2840 may be, for example, dynamic random access memory(DRAM), phase change memory (PCM), or a combination of the two. For atleast one embodiment, the controller hub 2820 communicates with theprocessor(s) 2810, 2815 via a multi-drop bus, such as a frontside bus(FSB), point-to-point interface such as QuickPath Interconnect (QPI), orsimilar connection 2895.

In one embodiment, the coprocessor 2845 is a special-purpose processor,such as, for example, a high-throughput MIC processor, a network orcommunication processor, compression engine, graphics processor, GPGPU,embedded processor, or the like. In one embodiment, controller hub 2820may include an integrated graphics accelerator.

There can be a variety of differences between the physical resources2810, 2815 in terms of a spectrum of metrics of merit includingarchitectural, microarchitectural, thermal, power consumptioncharacteristics, and the like.

In one embodiment, the processor 2810 executes instructions that controldata processing operations of a general type. Embedded within theinstructions may be coprocessor instructions. The processor 2810recognizes these coprocessor instructions as being of a type that shouldbe executed by the attached coprocessor 2845. Accordingly, the processor2810 issues these coprocessor instructions (or control signalsrepresenting coprocessor instructions) on a coprocessor bus or otherinterconnect, to coprocessor 2845. Coprocessor(s) 2845 accept andexecute the received coprocessor instructions.

Referring now to FIG. 20, shown is a block diagram of a first morespecific system 2900 in accordance with an embodiment of the presentinvention. As shown in FIG. 20, multiprocessor system 2900 is apoint-to-point interconnect system, and includes a first processor 2970and a second processor 2980 coupled via a point-to-point interconnect2950. Each of processors 2970 and 2980 may be some version of theprocessor 2700. In one embodiment of the invention, processors 2970 and2980 are respectively processors 2810 and 2815, while coprocessor 2938is coprocessor 2845. In another embodiment, processors 2970 and 2980 arerespectively processor 2810 coprocessor 2845.

Processors 2970 and 2980 are shown including integrated memorycontroller (IMC) units 2972 and 2982, respectively. Processor 2970 alsoincludes as part of its bus controller units point-to-point (P-P)interfaces 2976 and 2978; similarly, second processor 2980 includes P-Pinterfaces 2986 and 2988. Processors 2970, 2980 may exchange informationvia a point-to-point (P-P) interface 2950 using P-P interface circuits2978, 2988. As shown in FIG. 20, IMCs 2972 and 2982 couple theprocessors to respective memories, namely a memory 2932 and a memory2934, which may be portions of main memory locally attached to therespective processors.

Processors 2970, 2980 may each exchange information with a chipset 2990via individual P-P interfaces 2952, 2954 using point to point interfacecircuits 2976, 2994, 2986, 2998. Chipset 2990 may optionally exchangeinformation with the coprocessor 2938 via a high-performance interface2939. In one embodiment, the coprocessor 2938 is a special-purposeprocessor, such as, for example, a high-throughput MIC processor, anetwork or communication processor, compression engine, graphicsprocessor, GPGPU, embedded processor, or the like.

A shared cache (not shown) may be included in either processor oroutside of both processors, yet connected with the processors via P-Pinterconnect, such that either or both processors' local cacheinformation may be stored in the shared cache if a processor is placedinto a low power mode. Chipset 2990 may be coupled to a first bus 2916via an interface 2996. In one embodiment, first bus 2916 may be aPeripheral Component Interconnect (PCI) bus, or a bus such as a PCIExpress bus or another third generation I/O interconnect bus, althoughthe scope of the present invention is not so limited.

As shown in FIG. 20, various I/O devices 2914 may be coupled to firstbus 2916, along with a bus bridge 2918 which couples first bus 2916 to asecond bus 2920. In one embodiment, one or more additional processor(s)2915, such as coprocessors, high-throughput MIC processors, GPGPU's,accelerators (such as, e.g., graphics accelerators or digital signalprocessing (DSP) units), field programmable gate arrays, or any otherprocessor, are coupled to first bus 2916. In one embodiment, second bus2920 may be a low pin count (LPC) bus. Various devices may be coupled toa second bus 2920 including, for example, a keyboard and/or mouse 2922,communication devices 2927 and a storage unit 2928 such as a disk driveor other mass storage device which may include instructions/code anddata 2930, in one embodiment. Further, an audio I/O 2924 may be coupledto the second bus 2920. Note that other architectures are possible. Forexample, instead of the point-to-point architecture of FIG. 20, a systemmay implement a multi-drop bus or other such architecture.

Referring now to FIG. 21, shown is a block diagram of a second morespecific system 3000 in accordance with an embodiment of the presentinvention. Like elements in FIG. 21 and FIG. 22 bear like referencenumerals, and certain aspects of FIG. 20 have been omitted from FIG. 21in order to avoid obscuring other aspects of FIG. 21. FIG. 21illustrates that the processors 2970, 2980 may include integrated memoryand I/O control logic (“CL”) 2972 and 2982, respectively. Thus, the CL2972, 2982 include integrated memory controller units and include I/Ocontrol logic. FIG. 21 illustrates that not only are the memories 2932,2934 coupled to the CL 2972, 2982, but also that I/O devices 3014 arealso coupled to the control logic 2972, 2982. Legacy I/O devices 3015are coupled to the chipset 2990.

Referring now to FIG. 22, shown is a block diagram of a SoC 3100 inaccordance with an embodiment of the present invention. Similar elementsin FIG. 18 bear like reference numerals. Also, dashed lined boxes areoptional features on more advanced SoCs. In FIG. 22, an interconnectunit(s) 3102 is coupled to: an application processor 3110 which includesa set of one or more cores 202A-N and shared cache unit(s) 2706; asystem agent unit 2710; a bus controller unit(s) 2716; an integratedmemory controller unit(s) 2714; a set or one or more coprocessors 3120which may include integrated graphics logic, an image processor, anaudio processor, and a video processor; an static random access memory(SRAM) unit 3130; a direct memory access (DMA) unit 3132; and a displayunit 3140 for coupling to one or more external displays. In oneembodiment, the coprocessor(s) 3120 include a special-purpose processor,such as, for example, a network or communication processor, compressionengine, GPGPU, a high-throughput MIC processor, embedded processor, orthe like.

Embodiments of the mechanisms disclosed herein may be implemented inhardware, software, firmware, or a combination of such implementationapproaches. Embodiments of the invention may be implemented as computerprograms or program code executing on programmable systems comprising atleast one processor, a storage system (including volatile andnon-volatile memory and/or storage elements), at least one input device,and at least one output device.

Program code, such as code 2930 illustrated in FIG. 20, may be appliedto input instructions to perform the functions described herein andgenerate output information. The output information may be applied toone or more output devices, in known fashion. For purposes of thisapplication, a processing system includes any system that has aprocessor, such as, for example; a digital signal processor (DSP), amicrocontroller, an application specific integrated circuit (ASIC), or amicroprocessor.

The program code may be implemented in a high level procedural or objectoriented programming language to communicate with a processing system.The program code may also be implemented in assembly or machinelanguage, if desired. In fact, the mechanisms described herein are notlimited in scope to any particular programming language. In any case,the language may be a compiled or interpreted language.

One or more aspects of at least one embodiment may be implemented byrepresentative instructions stored on a machine-readable medium whichrepresents various logic within the processor, which when read by amachine causes the machine to fabricate logic to perform the techniquesdescribed herein. Such representations, known as “IP cores” may bestored on a tangible, machine readable medium and supplied to variouscustomers or manufacturing facilities to load into the fabricationmachines that actually make the logic or processor.

Such machine-readable storage media may include, without limitation,non-transitory, tangible arrangements of articles manufactured or formedby a machine or device, including storage media such as hard disks, anyother type of disk including floppy disks, optical disks, compact diskread-only memories (CD-ROMs), compact disk rewritable's (CD-RWs), andmagneto-optical disks, semiconductor devices such as read-only memories(ROMs), random access memories (RAMs) such as dynamic random accessmemories (DRAMs), static random access memories (SRAMs), erasableprogrammable read-only memories (EPROMs), flash memories, electricallyerasable programmable read-only memories (EEPROMs), phase change memory(PCM), magnetic or optical cards, or any other type of media suitablefor storing electronic instructions.

Accordingly, embodiments of the invention also include non-transitory,tangible machine-readable media containing instructions or containingdesign data, such as Hardware Description Language (HDL), which definesstructures, circuits, apparatuses, processors and/or system featuresdescribed herein. Such embodiments may also be referred to as programproducts.

In some cases, an instruction converter may be used to convert aninstruction from a source instruction set to a target instruction set.For example, the instruction converter may translate (e.g., using staticbinary translation, dynamic binary translation including dynamiccompilation), morph, emulate, or otherwise convert an instruction to oneor more other instructions to be processed by the core. The instructionconverter may be implemented in software, hardware, firmware, or acombination thereof. The instruction converter may be on processor, offprocessor, or part on and part off processor.

FIG. 23 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention. In the illustrated embodiment, the instructionconverter is a software instruction converter, although alternativelythe instruction converter may be implemented in software, firmware,hardware, or various combinations thereof. FIG. 23 shows a program in ahigh level language 3202 may be compiled using an x86 compiler 3204 togenerate x86 binary code 3206 that may be natively executed by aprocessor with at least one x86 instruction set core 3216. The processorwith at least one x86 instruction set core 3216 represents any processorthat can perform substantially the same functions as an Intel processorwith at least one x86 instruction set core by compatibly executing orotherwise processing (1) a substantial portion of the instruction set ofthe Intel x86 instruction set core or (2) object code versions ofapplications or other software targeted to run on an Intel processorwith at least one x86 instruction set core, in order to achievesubstantially the same result as an Intel processor with at least onex86 instruction set core. The x86 compiler 3204 represents a compilerthat is operable to generate x86 binary code 3206 (e.g., object code)that can, with or without additional linkage processing, be executed onthe processor with at least one x86 instruction set core 3216.Similarly, FIG. 23 shows the program in the high level language 3202 maybe compiled using an alternative instruction set compiler 3208 togenerate alternative instruction set binary code 3210 that may benatively executed by a processor without at least one x86 instructionset core 3214 (e.g., a processor with cores that execute the MIPSinstruction set of MIPS Technologies of Sunnyvale, Calif. and/or thatexecute the ARM instruction set of ARM Holdings of Sunnyvale, Calif.).The instruction converter 3212 is used to convert the x86 binary code3206 into code that may be natively executed by the processor without anx86 instruction set core 3214. This converted code is not likely to bethe same as the alternative instruction set binary code 3210 because aninstruction converter capable of this is difficult to make; however, theconverted code will accomplish the general operation and be made up ofinstructions from the alternative instruction set. Thus, the instructionconverter 3212 represents software, firmware, hardware, or a combinationthereof that, through emulation, simulation or any other process, allowsa processor or other electronic device that does not have an x86instruction set processor or core to execute the x86 binary code 3206.

According to one embodiment, a processor includes an instruction decoderto decode a first instruction to gather data elements from memory, thefirst instruction having a first operand specifying a first storagelocation and a second operand specifying a first memory address storinga plurality of data elements. The processor further includes anexecution unit coupled to the instruction decoder, in response to thefirst instruction, to read contiguous a first and a second of the dataelements from a memory location based on the first memory addressindicated by the second operand, and to store the first data element ina first entry of the first storage location and a second data element ina second entry of a second storage location corresponding to the firstentry of the first storage location. In one embodiment, the firstinstruction further comprises a third operand specifying the secondstorage location. In one embodiment, the instruction decoder furtherdecodes a second instruction having a third operand specifying thesecond storage location, and a fourth operand specifying a second memoryaddress, the second memory address being offset from the first memoryaddress by the size of a single data element. According to one aspect ofthe invention, the first instruction further comprises a prefixindicating to the instruction decoder and execution unit that the secondinstruction follows. In another embodiment, the execution unit predictsthe existence of the second instruction. In one embodiment, the firstentry of the first storage location is not contiguous to the secondentry of the second storage location, and wherein the second storagelocation is specified by the first operand. According to one embodiment,the first data element is stored in a third entry of a third storagelocation prior to being stored in the first entry of the first storagelocation, and the second data element is stored in a fourth entry of afourth storage location prior to being stored in the second entry of thesecond storage location.

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as those set forth in the claims below, refer to the actionand processes of a computer system, or similar electronic computingdevice, that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

The techniques shown in the figures can be implemented using code anddata stored and executed on one or more electronic devices. Suchelectronic devices store and communicate (internally and/or with otherelectronic devices over a network) code and data using computer-readablemedia, such as non-transitory computer-readable storage media (e.g.,magnetic disks; optical disks; random access memory; read only memory;flash memory devices; phase-change memory) and transitorycomputer-readable transmission media (e.g., electrical, optical,acoustical or other form of propagated signals—such as carrier waves,infrared signals, digital signals).

The processes or methods depicted in the preceding figures may beperformed by processing logic that comprises hardware (e.g. circuitry,dedicated logic, etc.), firmware, software (e.g., embodied on anon-transitory computer readable medium), or a combination of both.Although the processes or methods are described above in terms of somesequential operations, it should be appreciated that some of theoperations described may be performed in a different order. Moreover,some operations may be performed in parallel rather than sequentially.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific embodiments thereof. It will beevident that various modifications may be made thereto without departingfrom the broader spirit and scope of the invention as set forth in thefollowing claims. The specification and drawings are, accordingly, to beregarded in an illustrative sense rather than a restrictive sense.

What is claimed is:
 1. A processor, comprising: an instruction decoderto decode a first instruction to gather data elements from memory, thefirst instruction having a first operand specifying a first storagelocation and a second operand specifying a first memory address storinga plurality of data elements; an execution unit coupled to theinstruction decoder, in response to the first instruction, to readcontiguous a first and a second of the data elements from a memorylocation based on the first memory address indicated by the secondoperand, and to store the first data element in a first entry of thefirst storage location and a second data element in a second entry of asecond storage location corresponding to the first entry of the firststorage location.
 2. The processor of claim 1, wherein the firstinstruction further comprises a third operand specifying the secondstorage location.
 3. The processor of claim 1, wherein the instructiondecoder further decodes a second instruction having a third operandspecifying the second storage location, and a fourth operand specifyinga second memory address, the second memory address being offset from thefirst memory address by the size of a single data element.
 4. Theprocessor of claim 3, wherein the first instruction further comprises aprefix indicating to the instruction decoder and execution unit that thesecond instruction follows the first instruction.
 5. The processor ofclaim 3, wherein the execution unit predicts that the second instructionfollows the first instruction.
 6. The processor of claim 1, wherein thefirst entry of the first storage location is not contiguous to thesecond entry of the second storage location, and wherein the secondstorage location is specified by the first operand.
 7. The processor ofclaim 1, wherein the first data element is stored in a third entry of athird storage location prior to being stored in the first entry of thefirst storage location, and the second data element is stored in afourth entry of a fourth storage location prior to being stored in thesecond entry of the second storage location.
 8. A method, comprising:decoding a first instruction to gather data elements from memory, thefirst instruction having a first operand specifying a first storagelocation and a second operand specifying a first memory address storinga plurality of data elements; reading, in response to the firstinstruction, contiguous a first and a second of the data elements from amemory location based on the first memory address indicated by thesecond operand; and storing the first data element in a first entry ofthe first storage location and a second data element in a second entryof a second storage location corresponding to the first entry of thefirst storage location.
 9. The method of claim 8, wherein the firstinstruction further comprises a third operand specifying the secondstorage location.
 10. The method of claim 8, wherein the instructiondecoder further decodes a second instruction having a third operandspecifying the second storage location, and a fourth operand specifyinga second memory address, the second memory address being offset from thefirst memory address by the size of a single data element.
 11. Themethod of claim 10, wherein the first instruction further comprises aprefix indicating to the instruction decoder and execution unit that thesecond instruction follows the first instruction.
 12. The method ofclaim 10, wherein the execution unit predicts that the secondinstruction follows the first instruction.
 13. The method of claim 8,wherein the first entry of the first storage location is not contiguousto the second entry of the second storage location, and wherein thesecond storage location is specified by the first operand.
 14. Themethod of claim 8, wherein the first data element is stored in a thirdentry of a third storage location prior to being stored in the firstentry of the first storage location, and the second data element isstored in a fourth entry of a fourth storage location prior to beingstored in the second entry of the second storage location.